Gerry Adams and his MPs will not swear Commons oath
The republicans are currently denied access to offices and other privileges because of their refusal to swear an oath of allegiance to the Queen.
But the government believes Sinn Fein should have the same access and Commons leader Robin Cook told MPs a motion would go before the Commons next week.
Sinn Fein made gains at the general election and now has four MPs - more than the nationalist SDLP.
After months of speculation, the government and Sinn Fein have agreed the use of facilities at Westminster.
Sinn Fein has argued that, with a growing band of MPs, it is entitled to office space in Parliament, even though it has refused to take up its seats.
Speaking after a meeting with the prime minister on Thursday, the Sinn Fein President Gerry Adams said the people his party represented had been disadvantaged by not having the same facilities as others.
"I don't consider it, I have to say to be anything other than our entitlement as MPs," he said.
"We wish to use the offices and the facilities that we are entitled to both to further our broad political objectives here in Britain and to represent our constituents."
But the Speaker of the House of Commons, Michael Martin, is on record saying MPs will only be granted offices if they swear the oath of allegiance.
However, the government seems keen to relax the rules and Downing Street is in a hurry to change protocol.
The prime minister's official spokesman told reporters: "The government believes this is the right time.
"If we look at where we are in terms of the process, Sinn Fein are elected members of the Northern Ireland Assembly and are playing their part in the Northern Ireland Assembly."
He pointed also to Sinn Fein's role in government in Northern Ireland, as well as the start of decommissioning.
The spokesman added: "Peace processes are delicate flowers and they need constant feeding and therefore we need to keep talking to politicians in Northern Ireland."
Policy change
Mr Cook said Labour MPs would get a free vote when the issue is debated on Tuesday.
But, to a cries of "disgraceful" from opposition MPs, he argued it could not be right for Sinn Fein MP Martin McGuiness, to be education minister in Northern Ireland and yet be denied access to the Commons.
The Commons leader said the current restrictions only dated back to a ruling in 1997 by the then Speaker Betty Boothroyd.
Before then Sinn Fein MPs had access to the Commons and some of its services, he explained.
Earlier, shadow Northern Ireland secretary Quentin Davis accused the government of trying to "appease" republicans.
"What it would amount to is giving Sinn Fein an enormous propaganda victory, and if that wasn't enough giving them public money to boot, making a complete mockery of the rule of the House of Commons," he said.
Ulster Unionist MP Jeffrey Donaldson said the move showed the government was ignoring the wishes of parliament.
The Lagan Valley MP said: "For the past couple of days now the House of Commons and the House of Lords have been debating at length an anti-terrorism bill which proposes the most stringent measures against terrorist organisations.
"Yet here we have a government engaged in secret discussions - engaged in secret agreements that not even the speaker of the House of Commons is aware of."
No oath
However, Sinn Fein's Fermanagh and South Tyrone MP, Michelle Gildernew welcomed the move.
"As MPs, we're entitled to research facilities, to office facilities," she said.
"We have had a presence in London now for some time, I actually headed it up myself before I got elected to the assembly and we still provide a service to our constituents.
"That service should not be denied to us on the basis that we don't take an oath of allegiance to the British Queen and I as an Irish republican would never do that."