"Since the commencement of negotiations on the UK's exit from the European Union there have been a series of "leaks" and rumours, most of which are an attempt to exert pressure on the United Kingdom government in those talks", Mr Dodds said.
She said: 'Coming out of the customs union means that we will be free to have those deals, deals that suit the UK.
And on reports from the BBC suggesting the customs union issue could be treated as a motion of confidence in the Government, the spokesman said: "That report was an absolute mystery to me and I note that it quickly disappeared from the bulletins".
Thursday's vote on customs union membership in the House of Commons will not be binding but it will give an indication of how many Conservatives are willing to defy the government on the issue.
Number 10 has insisted the PM remains committed to leaving the customs union, in the face of reports at the weekend that her position may be softening.
The prime minister's problem is that her approach does not command a majority in parliament, where fears about the impact of leaving the customs union on British manufacturers and on the Border in Ireland are growing as Brexit approaches.
The EU published its first vision of the post-Brexit relationship at a summit in March.
And Mrs May insisted yesterday that she is still working towards implementing the proposals that were reportedly rejected by the European Union last week.
Monday's amendment would see Britain keep the EU Charter of Fundamental Rights, going against government plans to scrap it.
Speaking on Monday, Mrs May said her Government had put forward plans that will both "deliver a frictionless border" and "enable us to do trade deals around the rest of the world" outside the customs union.
"Consistently, polls have shown, that 60 to 70 per cent of people have accepted the result [of the Brexit vote] and want us to get on with it".
"Time to close the House of Lords down and kick [former Prime Minister David] Cameron and [Tony] Blair's mates out", blasted former UKIP leader Nigel Farage shortly later.
The peers voted 316 to 245 in favour of the latest amendment to government legislation now making its way through parliament, having delivered two stinging defeats last week.