Brown's new sweetener for voters - No10 chocolates

So when it came to meeting a nurse in her new flat, the Prime Minister had the perfect housewarming present – a box of special edition Downing Street chocolates.

He handed over the exclusive after-dinner mints to Zoe Broadhead, who had just moved into a housing development for key workers. And he even paid for them with his own cash.

It is believed to be the first time the mints – which have a drawing of No10 on each wrapper – have been seen publicly. Three hundred boxes are delivered to No10 each year for civil servants to buy and give to friends and relatives.

And Ms Broadhead, a 27-year-old intensive care nurse at the Whittington Hospital in North London, was delighted with her gift.

She said at her new home in Hornsey: "Mr Brown didn't say anything about the chocolates. He just handed them to me as he came into the room.

"He asked me about my decorating plans and joked about the colours I was going to paint my walls. The chocolates were a nice present, though I haven't eaten any of them yet."

The mint thins are made by House of Dorchester, whose factory is on the Duchy of Cornwall estate at Poundbury, Dorset – the ecologically friendly village designed for Prince Charles as an antidote to contemporary architecture.

They were the idea of businessman John Harrap, who runs craft and design firm Living Art at Bentley, Hampshire. He approached the manufacturers and created the design and packaging. Each white 150g box holds 16 individually wrapped mint thins – and the Downing Street arrangement is believed to have been running for three years.

Similar House of Dorchester chocolates, but without the Downing Street insignia, sell in Harrods, John Lewis and other stores for about £5.50.

Mr Harrap claims to supply a number of prestigious customers with personalised products. Other clients include the Stock Exchange, the Bank of England, Eton College, Westminster Abbey and accountants PricewaterhouseCoopers.

A No10 spokesman said last night: "Downing Street chocolates are available for members of staff to buy as gifts. On this occasion, the Prime Minister bought a box to give as a housewarming present. No cost to the taxpayer was incurred.

"The chocolates have been available for staff to buy for several years."

House of Dorchester marketing manager Katherine Ebbs said: "Living Art approached us with the idea for Downing Street chocolates. We deliver the boxes to Whitehall three times a year."