The pound fell to a one-month low against the U.S. dollar Wednesday after one of the country's biggest pollsters forecast a hung parliament in next week's U.K. elections.

The polling group YouGov said late Tuesday that Prime Minister Theresa May's Conservative party could lose as many as 20 seats at the June 8 vote, thus falling 16 seats short of an overall majority in the 650-seat chamber. The figures mirror a steadily eroding lead for May since the launch of her party's manifesto two week's ago and her handling of the deadly terrorist attack in Manchester on May 22.

"Walking the tightrope of public opinion in the aftermath of an atrocity is always difficult. Politicians do not often want to be seen to be capitalising on such events, at least not explicitly, and the momentum could well shift once again," YouGov said on its website. "What remains clear is that much of the underlying data still currently favours the Conservatives. They still enjoy a substantial lead on issues such as security, the economy and Brexit, while Theresa May is more favoured, by some distance, over Jeremy Corbyn when it comes to who the public think would make the best prime minister."

The pound fell around 0.57% to trade as low as 1.2784 against the greenback by 10:15 BST, the lowest since April 21. 

Investors may be betting that May's future as party leader will be jeopardised by a poor showing in next week's vote, particularly given the strength of her lead heading into the campaign in late April, when she called the snap election.

If so, there is a risk that she would be replaced by a more "hard-Brexit" advocate as the country enters exit negotiations with the European Union on June 19. 

Further pressure on the pound was added by news that U.K. mortgage approvals have fallen to a seven-month low, pointing to concerning signs that the housing market is bending under Brexit pressure.

Lenders approved 64,645 loans in April, the fewest since September, figures from the Bank of England show, despite low-interest rates on mortgages.

Mortgage lending increased by just £2.7 billion in April, the lowest growth since April 2016. The fall seems to be pointing to a slowdown in the U.K. housing market. According to lender Halifax, house prices had their first quarterly decline in more than four years in the three months through April, with prices declining 0.2%.