TOP Whitehall officials fear a major political crisis will erupt in London if too many concessions are made to Beijing in the negotiations over political reform. Senior sources expect a bigger backlash in the House of Commons than the Legislative Council, if Governor Chris Patten's blueprint is greatly watered down in the interests of reaching an acceptable compromise, with the British parliament denouncing the UK government for selling out the cause of democracy. Their misgivings were heightened yesterday when senior Tory backbencher Peter Temple Morris, former vice-chairman of the influential Foreign Affairs Committee, warned of a potential party rift over the issue. ''The great danger is that the Conservative Party may itself be split over the issue,'' he said. ''A minority might still seek to take the democratic road and, with only a small Conservative majority in the House, that could produce a very dangerous situation, reminiscent of what we went through over Maastricht.'' The political stakes have been raised in Westminster by United Democrat chairman Martin Lee Chu-ming's recent visit to London. Mr Lee claimed to have received undertakings from the opposition Labour and Liberal Democrats that any serious dilution of the Patten package would result in immediate questions in the House of Commons. An official source said a parliamentary debate on the outcome of the talks was now considered almost inevitable. ''There is a general underlying feeling across the House that Hong Kong is not quite coming out as we had hoped, that we might all have made a dreadful mistake,'' said Sir Russell Johnston, a leading Liberal in the cross-party Hong Kong parliamentary group. He confirmed any signs democracy had been seriously diluted by whatever agreement emerged from the talks would result in sharp questioning. Labour Party spokesman Allan Rogers was reluctant to be drawn into the outcome of the talks. ''We are supporting Governor Patten and believe his democracy proposals should have gone even further,'' he said. ''If a deal good enough for Hong Kong emerges, then we would not seek to be obstructive. But we shall certainly look critically at the outcome of the talks and raise whatever questions we then think necessary.'' Mr Temple Morris is one of several MPs who believe Britain's democracy initiative may have been misplaced from the start. He said a failure to sustain the Patten package in the talks with China ''would leave the government looking very vulnerable''. ''In Westminster, which basically wants a quiet life, we were given a democratic option over Hong Kong to which we could all agree,'' he said. ''With some concessions on the democracy front, that Legco could approve, they may get away with it. But it could be tight.'' The growing uncertainly over Westminster's response to a deal further adds to constraints on British negotiators in the talks, due to reopen with a ninth round in Beijing tomorrow. There are nevertheless high hopes in Whitehall that progress will be made during a hectic month of bargaining in September, with the 10th round of talks presently pencilled in to start in the week of September 6.