Leading left MP Ian Lavery has warned that the government's lobbying Bill us still a huge threat to democracy despite a few "tinkering" concessions.

Lib Dem MPs tamely trotted into government voting lobbies this week, ensuring that the Bill will bristle with dangers when it goes to its report stage and third reading in early October.

Mr Lavery urged no let-up in campaigning against the measure, which imposes curbs on trade unions and charities, while allowing 95 per cent of corporate lobbyists to pursue their murky trade.

MPs had received thousands of emails and letters from opponents of the Bill, said Mr Lavery, who also branded the "atrocious" Bill as an attack on the unions, bolted on to weak measures on corporate lobbying, plus anti-democratic curbs on activities of charities and campaigners in an election year.

Civil liberties campaigner Paul Flynn MP expressed astonishment that not a single Lib Dem MP had voted against clauses representing "a low, mean attack on charities," when even 11 Tories had voted against.

Mr Flynn intervened in the Commons committee stage debate to query why the Lib Dems were "so enthusiastic to embrace their own extinction."

Labour shadow business department minister Ian Murray protested against a new intrusion into trade union affairs via a proposed certification officer with extra powers to snoop into membership records.

The Conservative Party refused point-blank to reveal details of its membership, jibed Mr Murray.

"The only thing we know about Conservative Party membership is that the average age is 68, which might tell us something about where the party is going."

Mr Murray said trade unions were already heavily regulated and it was self-evident that unions wanted good membership records so that they could engage with members.

Left MP John McDonnell warned that it was part of government preparations against an upsurge of industrial action as "people get angry" about a recovery for the rich but a recession for the rest.