Ms McIntosh had hinted she might stand as an independent after being deselected as the Conservative candidate last year following an acrimonious row with members of her constituency association.
But flanked by party members and local councillors at the Pickering Conservative Club, she announced today she will step down quietly to ensure she does not damage the party’s chances in what could be a tight election.
Contesting the seat could have split the Conservative vote and given the UK Independence Party, which polled well in the area in last year’s European elections, an opportunity.
She said: “I believe this is the right time to put myself first and foremost on a different path. I believe that this election is going to be extremely difficult election, I think its going to be a very close-fought election, potentially a very divisive election. I do not wish to be the story in that election.”
She added: “I have been asked by many in this room and outside to stand locally in some capacity, obviously as an independent candidate. I am honoured to have been asked but I believe my place is within the Conservative Party and I would never have put personal ambition ahead of the best interests of the country in the long term and the short term which I can honestly say can only be best be served by another government led by this Prime Miniser, David Cameron.”
Ms McIntosh insisted she “bore no ill will” to those behind the move to deselect her and urged those disappointed by her treatment to continue to support the Conservatives.
But she pointedly said she would be campaigning in marginal constituencies rather than alongside her replacement in Thirsk and Malton, Kevin Hollinrake.
She also rejected suggestions she may have been offered other roles in return for standing down quietly.
But Ms McIntosh admitted the consequences of contesting the seat and losing had also played a part in her decision.
“You look at the numbers and there may be times when you think you want to poke someone in the eye and you turn around and you realise the only person you are going to poke in the eye is yourself and you are going to be stuck in the naughty corner.
“I have many friends in the Conservative Party and I hope I can use that to my own advantage in the future. Were I to burn my bridges and stand as an independent candidate I think you would find you’d have no friends at all.”
Ms McIntosh was elected to the European Parliament in 1989 before becoming MP for the Vale of York in 1997.
When that seat was lost as part of boundary changes at the 2010 election, she became the candidate for Thirsk and Malton and won with a majority of 11,281.
In the Commons she is the chairman of the Environment Food and Rural Affairs committee of MPs.