IT is a rare occasion when rival camps within the Legislative Council agree on an issue. It is even rarer when that issue involves constitutional matters. Yet this is precisely what occurred last night when conservative and liberal legislators spoke in one voice urging the Government to reveal the agenda and progress of the current Sino-British talks on Hongkong's future political reforms. That legislators feel the need to pressure the Government into releasing as much information as possible on the talks is indicative of the level of distrust that many in Hongkong feel when Britain and China sit down to discuss the territory's future. Recent history shows that Beijing and London have been too willing to negotiate Hongkong's future without the territory having a direct say. Yesterday's motion debate by United Democrat Mr Yeung Sum indicates the distrust is such that legislators believe only public scrutiny will keep the British side on the straight and narrow. To take Britain's promise of ''no secret deals'' at face value would be considered naive in the extreme, although both sides will no doubt be ready to leak details at sensitive moments if it suits their negotiating needs. While it is perfectly reasonable for legislators to want to be kept fully informed of the progress of the talks, they should be careful not to overstep the mark by seeking full disclosure of either side's negotiating position while the talks are underway. No sensible diplomatic negotiations can take place if either side is pressured to reveal its position at every turn. However, Hongkong people should be provided with regular briefings and joint communiques on the progress of the talks, if only as an assurance that no secret deals are being done. If Mr Chris Patten followed the United Democrats' advice and tabled his proposals in Legco tomorrow, China's inevitable exit from the talks would make a secret deal more, not less, likely. But fear that the Governor's constitutional plans will be quietly dropped is not the only motive. If it were, the Liberal Party would not be backing the United Democrats. The truth may be that both parties are trying to show they are nobody's lapdog. TheUnited Democrats want to show themselves independent of the Governor while the Liberals, not to be outdone, are determined to show themselves ready to jump on any publicity bandwagon going to prove their credentials to the Hongkong voter.