Barclays confirmed that it plans to lend state-backed mortgages under the new phase of Help to Buy, which was fired into action this week after the Government brought the launch date forward from January.
But the bank, which accounted for around 13% of mortgage lending last year, has not given any detail of what products are on offer.
The Government is offering £12 billion worth of guarantees under Help to Buy to encourage lenders to offer mortgages to credit-worthy home buyers with deposits as low as 5%.
So far, just a handful of lenders have launched products under the new phase of Help to Buy, with state-backed Royal Bank of Scotland, NatWest, Halifax and Bank of Scotland taking applications from this week.
Of the biggest mortgage lenders, only building society Nationwide, which had a mortgage lending share of around 15% last year, is still to decide whether or not it plans to take part.
Those other lenders who have confirmed their participation - Santander, HSBC, Lloyds Bank, Virgin Money and Aldermore - are expected to give more details about the deals they plan to offer nearer to their launch dates.
Some more products are expected to appear on the market later this year, followed by another wave of new deals in about January - the time the scheme was originally due to start.
Barclays' brief announcement on Twitter said: "We are pleased to confirm that Barclays will participate in the Help to Buy mortgage guarantee scheme."