ANNAPOLIS — As lawmakers and advocacy groups turn up the heat on bills they want vetoed, Gov. Martin O’Malley is beginning to signal his posture on several controversial measures passed during this year’s legislative session.

The General Assembly must deliver passed legislation within 20 days of Sine Die — April 27. The governor then must sign bills, reject them or let them become law without his signature within 30 days

O’Malley is being pressured to veto several bills, most notably one that extends a deadline to ban phosphorus from dishwashing detergents by six months to July 2010. O’Malley indicated on Wednesday that he is leaning toward signing the bill, despite efforts by Senate Judicial Proceedings Chairman Brian E. Frosh to veto it.

‘‘The way that some would look at it is that they’ve been doing it for so long, we should put an immediate stop to it,” O’Malley said on WTOP-AM’s ‘‘Ask the Governor” program. ‘‘The way others would look at it is that, after changing their practices and changing their products, that a six-month accommodation is not unreasonable, and I tend to come down on that side of the argument.”

The measure would push back implementation of a law signed last year that requires makers of household consumer products to remove goods that contain phosphorus from store shelves by January 2010. The effort to extend the deadline came after Procter & Gamble and other companies claimed they would not be able to meet the initial deadline. Phosphorus bans in other states all take effect in July 2010.

But Frosh (D-Dist. 16) of Bethesda is working with environmental groups pushing for a veto, saying the extra six months would allow 7.5 tons of phosphorus to seep into the Chesapeake Bay.

‘‘This is pollution that can be avoided,” he said. ‘‘Once you put phosphorus in the Bay, it’s very difficult to remediate and very expensive to remediate.”

But O’Malley said the six-month delay would not ‘‘make it or break it one way or another.”

Frosh plans to appeal to O’Malley again to veto a bill that would cost the state $1 million in Bay cleanup costs. That’s particularly troubling given that the legislature this year cut in half a $50 million Bay Trust Fund, he said.

‘‘This is an ‘increase the pollution’ bill,” said Brad S. Heavner, state director of Environment Maryland. ‘‘We worked so hard to reduce pollution, and here we have a success but we’re being forced to take a step backward.”

Other companies that make dishwashing detergents have already introduced or are developing phosphate-free products, so Ohio-based Procter & Gamble, which makes Cascade, should be able to comply with the January 2010 deadline, Frosh said.

‘‘To save the bay, we have asked sacrifices from our farmers and watermen,” he wrote in an April 16 letter to O’Malley. ‘‘We have imposed a flush tax on residents throughout the state to pay for sewage treatment plant upgrades. We have scraped together $25 million of new, scarce resources for bay cleanup with the promise of an additional $25 million next year. Given what we have asked of our citizens and the commitment we have made to the bay, it’s unfair and unwise to discard Maryland’s original deadline in order to indulge Proctor and Gamble, whose net sales of $76.5 billion last year more than doubled our entire state budget.”

Several organizations are lobbying for vetoes on other bills.

The Maryland Catholic Conference wants O’Malley to veto two bills that it says weaken the legal status of marriage in Maryland. The measures would grant hospital visitation rights to domestic partners and exempt them from paying property transfer taxes.

The group says it doesn’t oppose the purpose of the bills but fears they could lead to fraud because they require only evidence of a joint checking account and joint liability for a lease. Under the law, ‘‘relationship of mutual interdependence” affidavits need not be notarized or filed with the state.

‘‘Those relationships of mutual interdependence can easily be entered into and just as easily dissolved,” said Richard J. Dowling, the conference’s executive director, in a statement. ‘‘They assume scarce few of the obligations associated with marriages.”

The National Association of Enrolled Agents hopes O’Malley will reject the Maryland Individual Tax Preparers’ Act, which aims to crack down on unscrupulous accountants who aren’t properly licensed.

‘‘It’s a very reasonable bill that establishes very basic standards for licensing so that tax preparers have to demonstrate some knowledge of the tax code and have to sign the tax returns they prepare for profit so that they’re accountable,” said Comptroller Peter V.R. Franchot, whose office supported the measure. ‘‘Right now, you can be a palm reader and a tax preparer in the state.”

Last month, Franchot (D) joined consumer advocates at a rally for the bill outside a Silver Spring tax preparation business whose owner has been charged with filing fraudulent returns.

But H&R Block, the nation’s largest tax preparer, said it will result in higher fees for taxpayers and thousands of lost jobs. They worked with lawmakers on the measure for two years, but said last-minute amendments significantly altered the bill’s intent.

A company spokeswoman said their tax professionals must endure at least 104 hours of training and pass a rigorous exam on tax theory and law before seeing their first client. Returning tax preparers must take 50 more hours of continuing education each year.

Several business groups are petitioning O’Malley to veto the Flexible Leave Act, which requires employers who currently offer leave and who have more than 15 workers to provide paid time off to take care of sick family members.

‘‘It’s going to cause a lot of unintended consequences and lead to litigation and unnecessary conflict between employers and employees,” said Thomas S. Saquella, president of the Maryland Retailers Association. ‘‘We think employers can handle things as they are right now in a satisfactory manner and you really don’t need government getting into this.”

The bill will be particularly challenging for industries already dealing with staff shortages, such as community health providers, Saquella said.

Another high-profile veto request has involved efforts to keep so-called ‘‘alcopops” classified as a distilled spirit. Legislation passed the General Assembly this year that would have designated the fruity drinks, such as Mike’s Hard Lemonade, as beer, allowing them to be more widely distributed and taxed at a much lower rate than traditional liquors. The state levies a $1.50-per-gallon tax on distilled spirits and a 9-cents-per-gallon beer tax.

Advocates met with O’Malley several weeks ago, hours before he was expected to sign the bill. The governor said this week that he was still pondering the measure.

‘‘[I] wished I had known more when it was coming through the legislature,” he said, adding that he wanted more time for opponents to be heard. ‘‘I’m not sure it received the attention it should have received in the General Assembly.”

The Marin Institute, an alcohol industry watchdog, urged O’Malley to veto the ‘‘deceptive legislation” to discourage underage drinking. Several other states have already limited the sales of ‘‘alcopops” to state-run liquor stores only.

‘‘Big Alcohol is undermining these efforts by keeping the youth-friendly products cheap and readily available in convenience stores,” wrote Michael J. Scrippa, the institute’s advocacy director. ‘‘It’s a move that could have lasting impact on young people.”

Staff Writer Sean R. Sedam contributed to this report.