The government has restated its commitment to leaving the EU's custom Union - ahead of a symbolic vote on the issue this week.
And MPs will get their own chance to debate the issue on Thursday.
But a senior Downing Street source told the BBC the government's position would not change.
"We will not be staying in the customs union or joining a customs union," the source said.
BBC assistant political editor Norman Smith said Downing Street's move was an attempt to reassure Brexiteers worried about a U-turn following the Lords defeat and pressure from the EU.
A customs union is when countries agree to apply the same taxes on imports to goods from outside the union.
This means when goods have cleared customs in one country, they can be shipped to others in the union without further tariffs being imposed.
If the UK remains part of the customs union, it would be unable to strike trade deals with countries around the world.