The Mayo Fine Gael TD, Mr Michael Ring, is expected to give details today of his legal challenge to the Bill ending the dual mandate for members of the Oireachtas.
The Bill, known as the Local Government Bill, was signed into law by the President, Mrs McAleese, yesterday morning.
It means that TDs and senators will no longer be able to serve on local authorities after the local elections in the summer of next year. Mr Ring told The Irish Times yesterday: "I am consulting with my legal advisers about issuing proceedings as quickly as possible. I am confident I have cross-party support for this."
The poll-topping TD has been a trenchant critic of the Bill since it was first introduced in the Dáil by the Minister for the Environment, Mr Cullen.
In the last government, proposals to end the dual mandate were dropped following strong opposition from a number of Independent TDs, including Kerry South's Mr Jackie Healy-Rae, whose support was keeping the government in power.
Mr Healy-Rae said yesterday that he, and the Donegal North East Independent TD, Mr Niall Blaney, were considering if they would support Mr Ring's challenge. They are expected to discuss it this week when Mr Blaney returns from a trip abroad.
"It is an awful state of affairs that under this Bill members of the Oireachtas will lose their council seats, having been democratically elected by the people in 1999," said Mr Healy-Rae.