Senior Conservative MPs have questioned the proposed privatisation of Channel 4, with one former cabinet minister voicing “profound scepticism about the wisdom” of the plans.

Details of the Government’s proposals to sell off Channel 4 will be published on Thursday, culture minister Julia Lopez told MPs.

She said: “The Government is determined to protect the role of public service broadcasters in our nation’s economic, cultural and democratic life. And to make sure that they remain at the heart of our broadcasting system no matter what the future holds.

“So tomorrow we will be publishing a White Paper that proposes major reforms to our decades-old broadcasting regulations. Reforms that will put traditional broadcasters like the BBC, ITV and Channel 4 on an even playing field with Netflix, Amazon Prime and others and enable them to thrive in the streaming age.

“We will set out full details of our proposals when the White Paper is published and it is important to understand that the sale of Channel 4 is just one part of that major piece of reform.”

But Conservative Father of the House Sir Peter Bottomley (Worthing West) warned the “Government could do best by leaving it alone”.

He said: “Channel 4 is in the best state it’s been creatively and financially for decades.

“We were told earlier it was supposed to be able to compete with Netflix. Netflix’s share price is now 198 dollars, it was 700 dollars – that’s an enormous drop and it’s a loss-making, debt-ridden business.”

He called on the Government to “explain why they prefer to go to the US rather than have a state broadcaster which is independent of Government, and if those in Government think they don’t like it because it may occasionally in its news have criticised Government”.

Ms Lopez replied: “I think it’s important to understand the secretary of state (Nadine Dorries) and I went into this entire process with a very open mind.”

Conservative former cabinet minister Damian Green (Ashford) said: “(She) is aware of my profound scepticism about the wisdom of the course of action that the Government is taking on this.”

Another former cabinet minister, Jeremy Wright (Kenilworth and Southam), said: “(She) was right of course to say that previous secretaries of state have considered the privatisation of Channel 4, but she will also recognise not all of us were persuaded at the time it was the right thing to do.”

Julian Knight, Tory chairman of the Digital, Culture, Media and Sport Committee, asked: “I broadly welcome the concept of privatisation, but what assurances can the minister give me that this privatisation is a game worth the candle?”

The Conservative chairwoman of the Channel 4 all-party parliamentary group, Helen Grant (Maidstone and The Weald), said: “Channel 4 is a prized national asset. It was created by Margaret Thatcher 40 years ago. It puts public service before profit and it continues to be sustainable.

“So why is the Government failing to consider Channel 4’s detailed plans to address the Government’s concerns?”

Labour warned that Channel 4 would be “gobbled up” by US streaming giants if sold off, and criticised the Government for announcing details of the sale as the session of Parliament is expected to end.

Asking an urgent question, shadow culture secretary Lucy Powell said: “The sell-off of Channel 4 is an important matter for Parliament, yet instead of a statement we had announcement by tweet during recess and, now we hear, a White Paper to be published tomorrow when we won’t be here and there won’t be an opportunity for statements.

“And where is the secretary of state to defend her policy today? It is a pattern and it is a disgrace.”

Ms Powell questioned the reason for the sale, telling MPs: “Is it to help level up the country? Well given that Channel 4 commissions half their budget outside London, creating a pipeline of talent across the nations and regions, and stimulates the creative economy in places like Leeds, Glasgow and Bristol, of course it is not.

“Is it to create more British jobs in our world-leading creative industries? She and I both know that likely buyers are going to be the big US media companies, looking for a shop window for their own content.

“She says the sell-off is needed to help Channel 4 compete with the likes of Netflix and Amazon – the truth is it will be gobbled up by them.”

Conservative MP Neil Hudson (Penrith and The Border) described public service broadcasters, such as Channel 4, as “treasured national assets” and highlighted their importance to rural areas, adding: “Please, please can I urge the Government to rethink this Channel 4 privatisation idea.”