Dr James Sung Lap-kung, a City University political scientist, said that Ip, as chairwoman of the New People's Party and a former security minister, had built a clear image for her party: it is government-friendly but will exercise checks and balances on the administration when it matters. 'She is sending a clear message to the voters that her party would not blindly follow the government,' he said. 'This can help her party in its debut in November's district polls.'

Ip has been strongly advocating consultation and is a harsh critic of the government's performance in tackling the controversy.

The administration has proposed that midterm vacancies for directly elected Legislative Council seats should be filled by people from the same party as the former incumbent or, if the party list is exhausted, the next-best-placed candidate in the previous election.

The government aims to stop lawmakers resigning seats to trigger by-elections. Some pan-democrats did so last year over electoral reform, hoping the by-elections would serve as a de facto referendum on the pace and scope of democratisation.

'If the government wants to defuse the bomb, it had better make use of the summer recess to consult people,' Ip said on Saturday.

She also indirectly jibed at the performance of Secretary for Mainland and Constitutional Affairs Stephen Lam Sui-lung. 'You people shouldn't humiliate him. It's just a job for him,' she said on Sunday. She came under similar fire when promoting the national security legislation as security chief in 2003.

Sung said the DAB and the Federation of Trade Unions - staunch government supporters - would suffer after the government U-turn. 'The two parties have been positioning themselves as part of the ruling coalition, so the sudden U-turn is a kick in the teeth for them,' he said.

As late as Sunday, DAB chairman Tam Yiu-chung was still saying that the bill had to be passed on July 13 to ensure that district council candidates - and possibly also hopefuls for the new district council functional seats - were informed of the changed electoral rules. Tam said yesterday: 'Some members of the Legco bills committee want more consultation. The problem of not informing the district poll candidates of the rules remains ... so they should take different cases into consideration.'

FTU lawmaker Wong Kwok-kin had also said that deferring voting on a by-election ban was impractical.

Professional Forum's Dr Priscilla Leung Mei-fun faces political pressure too, as the Kowloon West lawmaker was the first to suggest banning by-elections, to prevent the so-called referendum loophole. She remained undecided on how to vote on the bill before the government announced the U-turn yesterday.

There is pressure, too, on constitutional minister Lam, who now faces calls to step down. Professor Ma Ngok, a political scientist at Chinese University, said he should step down to shoulder political responsibility for mishandling the legislation.

But Democratic Party lawmaker Cheung Man-kwong said even resignation by Lam could not solve the core problem. 'Throughout the whole controversy, Lam is Beijing's puppet and messenger only,' he said.