June 13 (Reuters) - Britain's housebuilders are disappointed with what they see as a lack of radical measures to tackle the country's housing shortage in the election manifestoes of both major parties, industry executives said on Thursday.

At its manifesto launch, the Labour Party confirmed its plans to build 1.5 million new homes, just short of the 1.6 million homes over the next five years promised to voters by the Conservatives on Tuesday. The election will be held on July 4.

The average British house price hit a record high in May and first-time homebuyers are facing the toughest financial environment in 70 years, according to a recent report by the Building Societies Association.

"The land supply side is very constrained and regardless of which party wins the election, this will not change quickly," Crest Nicholson's CEO Peter Truscott told analysts after the company reported a slump in first-half earnings.

"The planning system operates at a snail's pace," he added.

Clare Miller, the CEO of Clarion Housing, the UK's largest housing association, cautiously welcomed plans by both parties to bring forward investment in building new homes.

"In the end, it is action, not words, that matters," she said.

Although both parties had set similar targets, some analysts said Labour was prepared to be more radical to achieve its housing aims.

"Labour would address the planning system more aggressively, including a more strategic approach to the green belt and also a seemingly greater focus on social and affordable housing provision," said Aynsley Lammin, housing analyst at Investec.

The ruling Conservative party said in its manifesto that stamp duty - a tax paid on the purchase of property and land over a certain value - would be permanently abolished for first-time buyers on homes worth up to 425,000 pounds ($541,000).

The current exemption on stamp duty for first-time buyers is due to expire at the end of March 2025. (Reporting by Aby Jose Koilparambil in Bengaluru; Editing by Matt Scuffham and Paul Simao)