Reflecting growing concern among the European allies about the extent and harshness of the continuing military crackdown in Poland, the British foreign secretary, Lord Carrington, demanded the release today of the thousands of Poles believed to have been arrested and "an early resumption of the process of negotiation and conciliation."

Reporting to the European Parliament in Strasbourg in Britain's role as current president of the European Community, Carrington called the situation in Poland "a man-made disaster on a colossal scale."

His remarks, couched in significantly stronger language than a formal collective statement on Poland by the foreign ministers of the 10 Common Market countries here just two days ago, were inserted into his speech today at the last minute after consultations with other European governments.

European diplomatic sources said they reflected "escalating concern" about events in Poland, particularly the reported numbers of arrests, injuries and possibly deaths, apparent efforts to eradicate completely all trace of the Solidarity movement, and the absence of any evidence of negotiations with Solidarity's leadership or the Catholic Church hierarchy.

This has cast great doubt, these sources said, on the assurances of the Polish leader, Gen. Wojciech Jaruzelski, that the repressive measures would be short-lived and would not completely reverse the process of political reform in Poland. Western European leaders and diplomats had placed considerable emphasis on these assurances in their initially cautious, low-key "wait-and-see" response to the crisis.

Carrington repeated that "there must be no foreign interference whatever." He added, however, that there also "must be an early resumption of the process of negotiation and conciliation, including the release of those in detention. That alone can produce a solution to Poland's problem."

Meanwhile, French Prime Minister Pierre Mauroy confirmed reports Wednesday that he had told a French socialist union leader that French Embassy reports from Warsaw were quoting reports that nine persons had been killed since Sunday and anywhere between 40,000 and 45,000 had been detained, Washington Post correspondent Loren Jenkins reported from Paris.

[Mauroy told reporters today that he would not have divulged those figures if he did not consider the source reliable. He said that since he released that information he had received new reports of "higher figures" of arrests and casualties, but he did not elaborate.]

French Foreign Minister Claude Cheysson, meanwhile, told the National Assembly's foreign affairs committee that he had received assurances from Polish authorities that they did not intend to renounce the Gdansk agreements signed in the summer of 1980 that gave legal recognition to the Solidarity movement as a trade union, and gave Polish workers the right to strike and have access to the Polish media.