Bookmaker Betfair has revealed odds on a Tory overall majority have started to lengthen.
This follows new polling data from YouGov which suggests the Conservatives could lose 30 seats in next week's election, bringing their total to 310 - 16 shy of the 326 required to hold a majority.
The same poll forecast a gain of 28 seats for Labour.
Tonight's YouGov data, which will be updated daily between now and polling day, based on complex model and 7,000 sample over 7 days pic.twitter.com/MzpXXifBFX— Sam Coates Times (@SamCoatesTimes) May 30, 2017
While a Conservative overall majority is still odds-on at 1/5 on Betfair Exchange, just one week ago it was 1/11. Odds on an outcome of no overall majority are now at 6/1, in from 13/1 a week ago.
For bets on the size of a Conservative majority, a 150-174 seat majority is "well-backed as the favourite", with odds going as low as 3/1. However, Betfair said, that is now out to 10/1, with 50-74 seats at 6/1 and 25-49 seats at 7/1.
“Theresa May called this election with the aim of increasing the size of the Tory majority, so to actually lose their majority would be a monumental disaster," said Betfair spokesperson Katie Baylis.
"While punters on the Exchange are still backing a majority, there is certainly not as much backing for that as there was just a week or so ago."