The government is scrambling to save its plans for rent caps, after a major error was exposed in the legislation.

Fine Gael and Fianna Fail had earlier agreed to stick with a 4% rent gap, but to speed up their introduction in other urban and commuter areas.

However a drafting error means that the 4% cap could be doubled to 8 per cent immediately after the end of the current two-year rent freeze.

The error was spotted by Sinn Féin's Eoin Ó Broin, who called it a "major oversight".

The so-called rent 'pressure zones' look like being extended to include Limerick, Galway and Waterford cities in the New Year - as well as towns in Louth, Meath, Kildare and Wicklow.

But other opposition parties say it is a sell-out of renters.

After rows, crises and the possibility of a vacuum leaving renters open to any hike come the new year, the Dáil is finally to begin passing the legislation.

Fianna Fáil had raised objections, but has now climbed down and agreed to the proposed 4% cap in Dublin and Cork city.

People Before Profit deputy Richard Boyd Barrett says it is a sell out:

"So it's more evictions, more affordability, more crisis in the rental sector as a result of a dirty deal between Fianna Fáil and Fine Gael", he said.

The legislation will not automatically extend the rent pressure zones - but Housing Minister Simon Coveney is committing to look at other cities and towns in the Dublin commuter belt early in the New Year.

"We will be looking at counties like Meath, Louth, Kildare, Wicklow; and we will be looking at cities like Waterford, Limerick and Galway - and areas continuous to Cork city as they are the obvious likely areas to see new rent pressure zones" he said.

The debate will continue tonight and is likely to continue tomorrow afternoon.

Mr Coveney initially pulled the legislation from the Dáil business, saying he was not prepared to preside over flawed legislation.

"I cannot agree to take a Government bill in Government time if I do not know what the outcome is going to be at report stage," he told the Dáil earlier.

The legislation was then put back on the agenda and be debated until late tonight, and again tomorrow if necessary.

The initial postponement of the debate drew objection from opposition parties.

Fine Gael had indicated it would abandon the proposals unless Fianna Fáil agreed to set the cap at 4%.

Fine Gael said it would not back down from the proposed cap - saying that if it went any lower, landlords will be scared off.

However, Fianna Fáil had said the 4% was too high.