BIRMINGHAM, Britain, Oct. 2 (Xinhua) -- Former foreign secretary, and one time London mayor, Boris Johnson called on Prime Minister Theresa May Tuesday to abandon her so-called Chequers plan for a future trading deal with the European Union.

On the eve of May's keynote speech to the Conservative Party Conference in Birmingham, Johnson laid into the proposed Brexit blueprint and said the British public would be unforgiving if the government got it wrong.

The 1,000 seat auditorium was packed at a conference friend meeting which Johnson addressed, earning a rousing standing ovation. Commenators later said Johnson's "chuck Chequers" message was a direct challenge to May.

Sitting in the front row was former Brexit Secretary David Davis who, along with Johnson, resigned hours after May unveiled her Brexit blueprint after a ministerial meeting at Chequers, her country house retreat.

Johnson concluded his speech with the message: "If we get it wrong we will be punished. And if we get it right we can have a glorious future. This government will then be remembered for having done something brave and right and remarkable and in accordance with the wishes of the people."

Johnson said if the right deal with Brussels was agreed it could be win-win for both sides of the Channel.

He added: "If we get it wrong - if we bottle Brexit now - believe me, the people of this country will find it hard to forgive."

He said: "If we cheat the electorate - and Chequers is a cheat - we will escalate the sense of mistrust. We will give credence to those who cry betrayal, and I am afraid we will make it more likely that the ultimate beneficiary of the chequers deal will be the far right."

Johnson told the audience that if the Chequers deal is agreed it will only embolden those now calling for a second referendum.

"These are the same people who explicitly told the electorate that there was no going back, that voting leave meant leaving the customs union and the single market, and that there was no way they would be asked again. They are now cynically campaigning to do just that, in a way that would be disastrous for trust in politics. People would see that they would be simply being asked to vote again until they give the answer the Remainers want."

Johnson said he has watched the EU professionally for 30 years, adding: "every time a referendum goes against the federalist movement, I have seen how the centripetal forces lock on and slowly the offending country is winched back into place."

May is expected to tell conference delegates Wednesday that her Chequers proposal is the only realistic deal with Brussels.