Cornwall councillors will again be asked to oppose plans which could see an MP having to represent people in Cornwall and Devon.

The proposal for a so-called Devonwall MP have been on the cards since about 2010 when plans were first revealed to cut the number of MPs across the country from 650 to 600.

Under the plans, not only would the number of MPs be cut but there would also be an attempt to equalise the number of people represented in each constituency.

As a result the Boundary Commission has long proposed that this would mean there would have to be one constituency which straddles the border of Cornwall and Devon – creating Devonwall.

The latest proposals from the Boundary Commission are set to be published this month and are expected to include a Devonwall constituency which would cover parts of North Cornwall and North Devon.

In readiness, Cornwall councillors have tabled a motion which will go before Tuesday’s full council meeting calling on members to cement their opposition to Devonwall.

The motion, tabled by Liberal Democrat councillor Mathew McCarthy and seconded by Councillor Jesse Foot, recommends that the council: “Reaffirms its complete opposition to this because of its violation of the integrity of Cornwall as a distinct region.

“Believes this is contrary to the spirit of the Framework Convention for the Protection of National Minorities.

“Anticipates that legislation to implement these recommendations will be put before Parliament shortly.

“Notes and welcomes the request by the MP for St Austell and Newquay for a free vote in the House of Commons. Endorses the view that political parties should have free votes on major constitutional issues.

“Asks the Members of Parliament representing Cornwall to use their influence to secure appropriate amendments to the bill but, if necessary, ultimately to oppose the legislation.

“Resolves to write to local MPs, members of the House of Lords with Cornish connections and the Government on this basis and asks the Leader of the Council to raise this at the next quarterly meeting with Cornwall’s MPs.”

Devonwall objectors have long campaigned against the move and say the historic border of Cornwall should be treated the same as borders in Scotland and Wales.

And support for the campaign against Devonwall has crossed party political boundaries, with politicians from the Conservatives, Labour, Liberal Democrats, Mebyon Kernow and independents uniting.

Last year the Boundary Commission said it had listened to the objections but no viable alternative had been offered.

It said: “There was support for our proposed constituencies, but also many objections to the creation of a so-called ‘Devonwall’ cross-county constituency, as detailed previously in this report.

“Many of those who objected to a cross-county constituency did not submit a counter-proposal to create five constituencies wholly within Cornwall and the Isles of Scilly, each with an electorate within the permitted electorate range.

“It was argued that Cornwall was a separate entity to the rest of England and should be treated in the same way as Northern Ireland, Scotland and Wales in terms of the review.

“Our assistant commissioners were sympathetic to the arguments against a cross-county constituency between Cornwall and Devon, but accepted that the statutory rules left them with no choice but to recommend such a constituency.”

Cornwall Council will meet on Tuesday at 10.30am.