Nicky Morgan said the upcoming Tory conference must be used as an opportunity to set a clear vision for a thriving post-Brexit UK.
Morgan Morgan, Loughborough's Conservative MP, cited a series of bids and bans on the Prime Minister's upcoming speech at the Crunch conference.
She said that Ms. May should carefully weigh every single word she uses in her speech and avoid contentious issues at any cost.
Ms. Morgan, who is also chairwoman of the powerful Treasury Committee, said Ms. May should treat British voters as "adults" and confront them with a clear and calm explanation of the government's recent decisions on Brexit. What will happen next?
My prevailing impression of talking to voters and others about the break is that the British public is overwhelmingly tired with Brexit
She wrote for the Conservative Home website: "[Mrs May] must clearly state where the Brexit negotiations are, why she made the decisions she has – and where she expects them to go.
"The British must be treated as adults as Brexit unfolds, and they must live with them as much as possible to keep them on the side."
Morgan's position on the prime minister's speech comes after months of operations with her constituents, who, she says, are "tired of Brexit."
She said, "My predominant impression of conversations during the pause with voters and others is that the British public is overwhelmingly tired with Brexit.
Theresa May has to hold a perfect speech at the Conservative Party conference, Nicky Morgan said
"The most commonly used phrase was" just keep going – and then keep going with everything our government needs to do ".
"So Mrs. May's speech in Birmingham does not have to be long or complicated.
"But it must come from the heart – and talk about the heads of party members and the media to the people with whom they identify most: voters in the middle of the street."
The speech, Ms. Morgan continued, should be written by the Prime Minister himself in order to have a greater impact on the public.
The Conservative Party conference will take place between September 30 and October 3, just days before the unofficial deadline set by the United Kingdom and the EU to sign a Brexit treaty.
Theresa May's Checkers plan faces tough opposition from MPs who support a tough Brexit
British officials brought to Brussels a possible agreement based on the much-criticized Checkers plan, which could produce a so-called soft Brexit that was frowned upon by hardline Brexitians.
The remain-backing MP argued that it would be a waste of time to attack the Tory rebels or "take over" Boris Johnson's final comments.
Similarly, the speech on the next parliamentary elections could harm the Prime Minister.
Ms. Morgan said: "We are told that it sets out how the Prime Minister wants to win the 2022 election for the Conservatives.
"If that's right, that's the wrong approach, because, as investigations by Party members and supporters have shown, Ms. May will not lead the Conservatives into the 2022 elections.
Boris Johnson made a comparison between Checkers' plan and a "suicide vest"
"Such an approach would therefore be a waste of one of her last chances to live up to her status as prime minister and the legacy she wishes to leave to the party."
Parliament's comment comes after comparing Mrs Johnson's Brexit strategy with Mrs. May and a "suicide vest" and growing rumors that could support Brexit-supporting MPs in a leadership bid against Ms. May.
However, a successful speech could strengthen the position of the main leader, Ms. Morgan said.
She continued, "The prime minister is in a very difficult situation.
Nicky Morgan MP is the chairman of the powerful Treasury Select Committee
"But most decent people understand that and wish her well.
"Her speech can pay back her confidence and make sure her difficult situation does not become impossible.
"If possible, she has to write that herself.
"And we have to see the prime minister who danced and smiled in South Africa – not the PMQ version."