Franklin's Gardens is not big enough to hold Heineken Cup quarter-finals
Northampton Saints may have to play future games at stadium:MK, the home of Milton Keynes Dons, according to chief executive Allan Robson.
Robson has warned that Franklin's Gardens' 13,500 capacity is too small for some potential fixtures.
He told BBC Radio Northampton: "In the Heineken Cup, if we make the quarter-finals we will be forced to play at a 15,000-seater stadium.
"So we will be going to Milton Keynes for that match."
The club announced plans in May 2009 to expand their ground capacity to 17,500, a move that would be funded by selling land owned by Saints to supermarket giant Asda.
But Robson says Northampton Borough Council have intimated they would block any such project.
"There will be no alternative if we don't come up with that planning permission," he said.
"Really we need help from the Northampton Borough Council on behalf of the community."
The issue of the Borough is that the central government has a planning policy that you should not have developments out of town which would have an adverse affect on the town centre
However Councillor David Perkins insists no planning application has yet to be received.
He said: "We've had two meetings with representatives of their board, in December 2009 and June of this year.
"We had made it clear that we wanted to support what the rugby club were doing and we would do what we could to help them.
"In regard to the planning permission, clearly you have to put in a planning application before you can get permission.
"At the last meeting we were told a planning application was imminently about to be submitted, as yet we have not received one."
Cllr Perkins went on to imply an application would not necessarily be successful.
"The issue of the Borough is that the central government has a planning policy that you should not have developments out of town which would have an adverse affect on the town centre," he said.
"Clearly we wish to defend the town centre and we support that policy."
The news comes as Northampton Saints plc, the club's holding company, has declared a net profit for the financial year of £521,048 after tax.
The figure is up from the £16,283 recorded in 2009 - a profit over 30 times greater.
It is the 10th consecutive season of profit for the Premiership semi-finalists, with their turnover a record £12.033m.