Labour is calling on the government to tighten the law around lobbying amid continued questions over David Cameron's links to collapsed finance firm Greensill Capital.
A watchdog cleared the former prime minister of unregistered lobbying after it was found he did not have to declare his work on behalf of the company.
Shadow Cabinet Office minister Rachel Reeves said the rules were "toothless".
Ministers say the lobbying process has become significantly more transparent.
Ms Reeves's comments come after it emerged Mr Cameron tried to lobby government figures to increase Greensill Capital's access to emergency Covid loans, when the company collapsed into administration.
Under the current rules, Mr Cameron was not classed as an outside "consultant" lobbyist so did not have to make a declaration when he went to work for Greensill after leaving office.
Ms Reeves said it was "crucial" ministers include legislation in next month's Queen's Speech to expand the register of consultant lobbyists to include so-called "in house" lobbyists like Mr Cameron.
There have also been claims the Greensill founder, Lex Greensill, benefitted from "privileged access" to Whitehall, gained during Mr Cameron's time at Downing Street.
Neither Mr Cameron or Mr Greensill have commented.
The government said it has "significantly increased transparency since 2010 - routinely publishing details of contracts, spending and meetings, and introducing a statutory register of consultant lobbyists".
It said further changes are planned to make sure "the highest standards" are upheld in public life.
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