Britain's Deputy Leader of the Labour Party Tom Watson appears on BBC TV's The Andrew Marr Show in London, Britain, March 31, 2019. Jeff Overs/BBC/Handout via REUTERS

LONDON (Reuters) - Britain’s opposition Labour Party can do a deal with Prime Minister Theresa May on customs arrangements but the party might not support any Brexit proposal unless it includes a new referendum, deputy leader Tom Watson said.

Labour is meeting the government for a third day of talks on a possible solution to the impasse over Brexit, with May seeking a further delay while she seeks to find a deal that can get parliamentary support.

“We’re genuinely going in with an open mind, but if it comes out of that process without the idea of a confirmatory ballot, I think we would have a bit of difficulty with our parliamentary party,” Watson said in an interview with BBC radio, adding that talks on customs arrangements could be easier.

“Our red line... is a form of customs union. It does seem to me there could be some meeting of minds there, but let’s see where the talks go today.”