Theresa May has been facing increasing pressure from both pro-Brexit and pro-Remain members of her Cabinet, risking a rebellion over her European Union Withdrawal Bill.
After Lord Maude suggested the Prime Minister does not have any factual influence on her MPs, Ms Coburn said: “So she’s in office but not in power.
“But you are saying she has really no power at her disposal to direct this in any way or show leadership.”
Lord Maude argued that being Mrs May the leader of a Government without a majority, Parliament ultimately holds power over her.
The former minister said: “She’s in office as a leader of a minority government that’s held in place by a small party and that has obvious limitations on your ability to get you will through.
“She can show leadership but at the end of it, no Prime Minister can do what the House of Commons doesn’t allow her to do.
That’s just how Parliamentary democracy works: if you have a decent, working majority then you can have a rebellion and you can still get your will through.
Tory rebels have accused the Prime Minister of backing down from a verbal promise to provide MPs with a meaningful vote in the event of a no deal Brexit.
Mrs May avoided almost certain defeat in the House of Commons on Tuesday by inviting potential rebels into her private office and assuring them that their concerns about having a “meaningful vote” on the final Brexit deal would be addressed.
However, the amendment to the EU Withdrawal Bill tabled on Thursday leaves Parliament facing a “deal or no deal” choice.
If MPs reject the agreement reached by Mrs May with Brussels – or if no deal has been obtained by January 21 – Parliament will be offered the opportunity only to vote on a “neutral motion” stating that it has considered a minister’s statement on the issue.
Crucially, the motion will be unamendable, meaning that MPs cannot insert a requirement for Mrs May to go back to the negotiating table, extend the Brexit transition or revoke the UK’s withdrawal under Article 50.