HOUSTON (AP) _ Republican platform writers under pressure from the White House today excised a section that denounced as a mistake the 1990 tax increase signed by the president.

The provision now says instead that the hike was recessionary and that the new taxes were insisted on by Democrats.

Bush's 1988 campaign pledge of no new taxes went by the boards when he signed a deficit-reduction agreement with Congress that raised taxes. He himself has called the move a mistake.

But campaign and White House officials were not pleased when the platform writers added a section Monday that said: ''Republicans believe that the taxes contained in the 1990 budget agreement were a mistake. ... We believe these tax increases should be repealed.''

Sponsor Vin Weber, a Minnesota congressman, tried Monday to remove the word ''mistake'' but other members of the economics panel voted him down.

''I think we have to eat a little humble pie,'' said Mary Kohler, a platform committee member from Wisconsin.

Campaign officials met with Weber and Rep. Robert Walker of Pennsylvania today to complain about the language. Right after that, the economics panel reconvened and adopted the revised provision.

Weber insisted the original had not been aimed at the president. But Charles Black, a senior campaign strategist, asked if the focus had been too pointed, responded: ''I have not heard other Republicans come out and say they made a mistake.''

Monday's attempt at damage control on taxes came as delegates stood firm on the platform's call for a constitutional amendment to ban abortion.

Dissenters were outnumbered by defenders of the provision 17-3 on the individual rights panel handling the abortion issue. The outcome was not expected to differ when the 107-member platform committee votes on the document this week.

The full committee was starting consideration of the inch-thick document today and hoped to complete it by Wednesday night. A floor vote is scheduled Monday, the first day of the Republican National Convention.

Bush's opposition to abortion made it virtually certain the anti-abortion plank would remain in the final party platform. Besides the constitutional amendment, the draft also reiterates the party's support for the appointment of anti-abortion judges and opposition to federal spending on poor women's abortions and organizations that advocate abortion.

The draft for 1992 is written in highly charged language that contrasts with the milder tone of 1988. It praises Bush and blames Democrats for events of the past four years. It also contains indirect attacks on Democratic nominee Bill Clinton for proposing tax hikes on the rich and swipes at his wife, Hillary, an influential lawyer and children's advocate.

One section condemns ''vocal advocates'' who believe ''children should be able to sue their parents over decisions about schooling, cosmetic surgery, employment and other family matters ... this is the ultimate agenda of contemporary socialism.''

The veiled reference was to Mrs. Clinton, who has written that children should be able to sue their parents in extreme cases where medical treatment or education is at stake. That panel also handed out copies of an unflattering article about Mrs. Clinton before its session.

There was equally inflammatory rhetoric in a section opposing statehood for the District of Columbia. The capital was called ''a national disgrace'' with one-party rule that has resulted in ''massive dependency, hellish crime and unremitting scandal.'' The GOP solution: closer congressional supervision, federal oversight of D.C. law enforcement, and tighter controls on the city's spending.

The rhetoric was found not only in the platform draft but also in the hallways of the convention center at impromptu press conferences.

Phyllis Schlafly, head of a group defending the anti-abortion plank, called her abortion-rights rivals ''a handful of country-club Republicans'' who have already deserted the party. ''There's a certain group of pro-abortion, rich Republican women who are pushing on this issue who may be lost,'' she said.

Two leaders of the abortion-rights contingent, Mary Dent Crisp and Ann Stone, accused party officials of heavy-handed tactics to keep dissidents in the fold and present a united front.

''It's a very tough job to turn the ship of state around,'' Stone said. ''Republicans are civil, respectful and don't buck the hierarchy. They're very loyal.''