BAA’s controversial plans for a second runway at Stansted will be sent to a public inquiry by ministers this week - but the company will at the same time be given permission for a big increase in passenger numbers at the Essex airport.

Numbers could rise from the present 23.5m to as many as 40m following ministers’ decision to scrap current restrictions and allow an increase in flights.

The move to a public inquiry on the £2.3 billion second runway means a final decision on whether it can go ahead is now not likely before 2011 at the earliest. Ruth Kelly, the transport secretary, is expected to announce the two Stansted decisions this week.

Supporters of airport expansion say the moves represent a significant step in implementing the government’s 2003 aviation white paper, which said congestion at southeast airports should be relieved by new runways at Stansted and Heathrow, with the Essex airport coming first.

Even if objections can be overcome, a new runway at Stansted is not likely to open before the middle of the next decade.

In the meantime, BAA has pushed to have the current limits on passenger numbers lifted. The Essex airport is at present limited to 25m passengers a year. Last year it handled 23.5m.

BAA wants the limit on passenger numbers scrapped, and replaced by a limit on the number of flights.

The airports group wants this increased from 241,000 a year to 261,000 a year. It says this should see Stansted grow to handle 35m passengers a year, while antiexpansion campaigners maintain that it will mean as many as 40m.

Uttlesford district council rejected the plan last year. It went to a public inquiry, which finished in October. A decision from the government has been expected since Christmas.

The inquiry on the new runway - which could eventually take Stansted up to 80m passengers - is expected to start next spring, and take up to a year. A final decision from the government could take another year.

Stop Stansted Expansion, a lobby group opposed to the new runway, said it was confident of winning the public inquiry.

“The final decision on this project will be taken not by this government but by the next one, and the Conservatives have long realised there is no economic case for doubling the size of Stansted,” a spokesman said.

“It also makes no sense as an investment for the owner of the airport, particularly when the owner is strapped for cash, as BAA is.”

Meanwhile, BAA revealed last week that it had started negotiations with bondholders which are crucial to its planned refinancing.

The company has asked the bondholders to agree to a rejig of the company’s structure.

BAA said the talks were progressing well, although it added that “certain aspects of the implementation of the permanent financing structure remain to be finalised”.

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