The British government announced changes today in regulation of Northern Ireland's prisons aimed at convincing Irish nationalist prisoners to abandon all forms of protest since the hunger strike's end last weekend.

Britain's new secretary for Ulster, James Prior, declared he is "seeking reconciliation and end to violence." He said prisoners will be allowed to wear their own clothes at all times and the government will take steps to increase opportunities for job training and education and for free-time association among prisoners.

To convicted Irish nationalist terrorists who agree to conform to prison rules, Prior offered time off for good behavior. Some prisoners had accumulated such time before the onset of the protests, only to see it canceled when they began. He said up to half of that time would be restored and "a handful" could be released immediately.

Prisoners also would be given more liberal mail, visitor and other privileges already available to conforming prisoners.

Prior's package fulfills several of the protesters' demands and closely resembles suggestions made by Irish Roman Catholic churchmen and politicians who sought to mediate an end to the hunger strike earlier. The changes continue prison reform in Northern Ireland that has gone beyond reforms in the rest of Britain.

Cardinal Tomas O'Fiaich, leader of Ireland's Roman Catholic Church, welcomed "the speed with which Prior has announced changes in prison conditions so soon after the ending of the hunger strike."

O'Fiaich, who has frequently criticized Prime Minister Margaret Thatcher's handling of the hunger strike and other problems of British rule in the province, said "the granting to prisoners of the right to wear their own clothes at all times is a fuller recognition of human dignity and should ease the situation in the prisons."

The only criticism of the reform came from some political leaders of Ulster's Protestant British loyalist majority. In the most vitriolic reaction, the Rev. Ian Paisley, leader of the hard-line Democratic Unionist Party, called the package "a complete sellout to those engaged in the campaign of murder against the Protestant community."

But Prior emphasized that the changes would not give the convicted terrorists special treatment, introduce "a political or military system of administration," or allow them to dictate their own conditions.

Prior said prisoners' demands that they be allowed to associate freely throughout each H-shaped cell block of the high-security Maze Prison outside Belfast, and determine their own prison work, will not be met. Prior agreed only to allow smaller groups of prisoners free association within two 25-man wings of each cell block, after physical and administrative changes are made, and to explore ways to be more flexible in assigning work.

The new government minister in charge of Northern Ireland's prisons under Prior, Lord Gowrie, will meet with Maze prisoners to explain the changes, if it becomes necessary, Prior said, but they are not negotiable.

Gowrie met last week with relatives of the last six hunger strikers. The families later helped end the protest by declaring they would authorize treatment to keep the prisoners alive if they did not end their fast voluntarily. Informed sources said Gowrie explained to them what the government might do if the hunger strike ended.

The first reaction to the package from militant Irish nationalists today was muted. Gerry Adams, Belfast leader of Provisional Sinn Fein, the public voice and political arm of the outlawed Provisional Irish Republican Army, to which most of the protesting prisoners belong, said the prisoners would decide whether they were satisfied. About 400 Irish nationalist prisoners in the Maze have been continuing the 5-year-old protest by refusing to wear prison clothes or do prison work.

"What is more certain, however, is that the right by the prisoners to wear their own clothes has been won by the deaths of the 10 H-block martyrs" during the 7-month hunger strike, Adams said.

The clothing issue had become symbolic of the impasse between the British government and Irish nationalists after a government decision in 1976 to imprison convicted terrorists like ordinary criminals rather than confining them in prisoner-of-war-style camps. About 350 Catholic Irish nationalists and Protestant British loyalist terrorists convicted before 1976 are still living in such camps.