Baroness Wheatcroft said Parliament should agree to trigger Article 50, kick-starting the Brexit process.
Her comments came the day after Prime Minister Theresa May pledged to trigger Article 50 before March next year, without parliamentary backing.
Attorney General Jeremy Wright will represent the Government in court this week as campaigners challenge this course of action.
Baroness Wheatcroft has sided with those arguing that Parliament should have its say.
She told the BBC Radio 4 Today programme that “Not everybody in the Conservative Party feels the same way as the Prime Minister”.
She added: “The people did say they were unhappy with the current situation. What they haven’t said is what they’d like to see as an alternative.
“Quite honestly, I think they should have an opportunity to look at what’s being offered before we commit to leaving the EU.”
Baroness Wheatcroft said she was “very confused” about Mrs May’s strategy, and what the balance would be between access to the single market and controls over immigration.
“It doesn’t feel very democratic to me to have one individual using the royal prerogative deciding exactly when we’re going to commit to that momentous path,” said Baroness Wheatcroft.
“This is surely something for the sovereignty of Parliament to have a say in, and not for the Prime Minister alone.
“The route forward is unclear. A second referendum is obviously a possibility. A general election at some stage is a possibility.
“But people need to have a view as to what it is they’re being offered.”
In a speech to the Conservative Party conference, Mrs May accused those trying to get the issue voted on in Parliament of “subverting democracy”.
Mrs May said: “It is up to the Government to trigger Article 50 and the Government alone.
“When it legislated to establish the referendum, Parliament put the decision to leave or remain inside the EU in the hands of the people. And the people gave their answer with emphatic clarity.
“So now it is up to the Government not to question, quibble or backslide on what we have been instructed to do, but to get on with the job.
“Because those people who argue that Article 50 can only be triggered after agreement in both Houses of Parliament are not standing up for democracy, they’re trying to subvert it.
“They’re not trying to get Brexit right, they’re trying to kill it by delaying it. They are insulting the intelligence of the British people.”
David Greene is senior partner of Edwin Coe LLP, which is acting for Deir Santos, one of the applicants in the Article 50 challenge.
He told the Today programme: “After serving the Article 50 notice, there are two years set and after those two years the United Kingdom leaves the European Union.
“So, Members of Parliament have little choice in that process.
“What we say is that, in fact, Parliament should be enjoined much earlier, i.e. before the serving of the Article 50 notice, so that they can decide when they want to serve it and what are the terms of service.
“We say that, in essence, you can only serve the Article 50 notice, withdrawing from the European Union, because it was Parliament that took us into the European Communities Act.
“The Government says they can use royal prerogative. We say that simply cannot apply in these particular circumstances.”