The Prime Minister could be facing a defeat over extending Sunday shop opening times, with people in his own party saying they would vote against his plans.
Some MPs say the measure has already been dropped due to opposition.
The current trading rules for shops state that large shops can open for six hours on a Sunday. Smaller shops can be open all day. There was a previous attempt to extend the hours in 2016 but it was unsuccessful, also due to Tory rebels.
The Prime Minister wants to extend opening hours to help the economy recover.
However, his plans have been opposed by at least 50 Tory MPs, according to the Daily Telegraph, who have seen a letter from them to the PM.
The MPs write in their letter: "Sunday represents an important common day of rest, where families and communities can spend time together.
"Sunday is an especially important day for the millions of retail key workers that have been on the frontline during the nation’s response to the Covid-19 outbreak, feeding the nation and delivering for their local communities. 91 per cent of shop workers do not want longer Sunday trading hours in large stores.
"We have learnt from the outbreak the value of social connectivity. As a nation we spent more time with our families, talked to our neighbours, and our communities have come together to help the most vulnerable."
Many in the Labour Party are also against changing the rules, with Christian shadow Cabinet member, Jonathan Reynolds responding online: "Liberalising Sunday trading laws is opposed by trade unions, small businesses and most faith groups. That is a not a coalition easily beaten"
The letter is signed by Conservative MPs: Fiona Bruce, Andrew Selous, William Wragg, David Amess, Martin Vickers, David Jones, and Bob Blackman. It is also signed by MPs who remained anonymous because they joined Parliament in the last election and do not want to be targeted by party whips.
They write: "We stand squarely behind your ambition to stimulate economic growth and revitalise British high streets, but removing Sunday trading hours will not achieve this.
"It will harm local shops and high streets by displacing trade to large out of town retail parks and supermarkets. Instead the government should review the seven substantive reports developed since 2011, by government departments, industry leading experts, academics and parliamentarians, containing hundreds of recommendations, but none have recommended removing Sunday trading hours."