Stephen Byers, the former transport secretary, today insisted he had complied with the MPs' code of conduct after a group of Labour MPs were targeted in an elaborate sting operation in which journalists set up a bogus lobbying company and offered to pay them in return for political influence.

Byers, an arch Blairite, was filmed describing himself as a "bit like a sort of cab for hire" and offering to trade Westminster contacts for £3,000 to £5,000 a day.

Amid condemnation from senior cabinet ministers, the Labour party tried to limit the damage by saying some MPs were "mortified" by how stupid they had been, and promising a crackdown on lobbying by former ministers, rushing forward a manifesto pledge for tighter regulation and monitoring.

Others who were targeted in the undercover operation included former cabinet ministers Geoff Hoon and Patricia Hewitt. Margaret Moran, Labour MP for Luton South, was also involved.