Former ministers will be banned from lobbying the Government for five years under plans put forward by Labour.
Backers say the move will help to "clean up" Westminster after a string of high-profile lobbying scandals.
The rule change is expected to `be included in Labour's manifesto after being considered by its national policy forum in the summer.
It has been cautiously welcomed by lobbying firms following crunch meetings last week - but the party was urged to go even further.
Lobbying has been in the limelight after it emerged that former PM David Cameron had contacted officials on behalf of his employer Greensill Capital in 2020.
And ex-cabinet minister Owen Paterson was forced to quit as an MP in 2021 after he was found to have broken rules by lobbying for two companies.
Alastair McCapra, who heads the lobbyists' trade association the Chartered Institute of Public Relations (CIPR), said: "It is encouraging to see the Labour Party addressing the issue of lobbying that has tarnished our politics for so long.
"Their proposed five-point plan and Integrity and Ethics Commission is a huge step in the right direction and rightly focuses immediate concerns on the actions of those within Parliament and those who have recently left."
He added that the CIPR had met with Labour last week to discuss the proposals, and had advised the party that transparency around external lobbyists was "still missing" from its plans.
He said: "More needs to be done to proactively change the culture around transparency and accountability when it comes to lobbying."
Labour is also considering setting up an Integrity and Ethics Commission - which would be allowed to investigate ministers' behaviour without approval from the PM.
Currently ethics probes are only launched after getting a thumbs up from No10.
In the past the Advisory Committee on Business Appointments (Acoba) has prevented former ministers for taking positions that involve lobbying, but bans rarely last more than two years.
Labour deputy leader Angela Rayner has previously announced a lobbying crackdown after the Paterson scandal.
Mr Paterson resigned from the Commons following a row over his lobbying for two companies that employed him as a consultant.
Ms Rayner described the existing system for monitoring former ministers' new jobs as a "toothless watchdog" and promised to "close this revolving door for good".
In a speech to the party conference in 2021, she said those who break the rules would face financial sanctions.
"We will stop former ministers profiting from public office, and we will close this revolving door for good", she said.
"Public servants should serve the public without an eye on a cushy lobbying gig as soon as they leave."
Ms Rayner also took aim at Mr Cameron over the Greensill scandal, which saw the former prime minister informally lobby the Government on behalf of Australian financier Lex Greensill.
An inquiry later found Mr Cameron's actions had been within the rules and he had not been required to register as a lobbyist.
