Christmas shoppers heading across the Atlantic to pick up bargains are being warned against bringing too many gifts back to the UK.
The pound is at its strongest against the dollar since 1992
HM Revenue and Customs is reminding travellers they must declare gifts bought in the US totalling over £145.
If shoppers fail to declare their gifts and pay the required duty, they risk prosecution, officials say.
Bargain hunters are expected to flock to the US to take advantage of the best exchange rate since 1992.
Regulations say duty must be paid on goods, including gifts and souvenirs worth more than £145. Separately duty must be paid on tobacco, alcohol and cosmetic purchases beyond certain amounts.
The dollar is currently trading at $1.98 to the pound and is expected to trigger a rush to make the most of what is being dubbed the "two dollar pound".
Virgin Atlantic said passenger numbers to New York had risen by 20% on last year.
And British Airways added four additional flights to the US this week.
"The weak dollar has had a major impact," a Virgin Atlantic spokesman said.
But Customs bosses are warning shoppers not to get carried away.
HM Revenue and Customs is reminding travellers that up to 20% of duty can be levied on goods. On some items an additional VAT at 17.5% must also be paid.
A Customs spokeswoman said it was the responsibility of passengers to understand import limitations.
She said that it was "business as usual" at airports, where so far officers had not found more passengers arriving with high-value goods.
She added that a "common sense approach" would be adopted, as there were also other pressing issues for officers to deal with "such as firearms, Class A drugs and other prohibited items".
The pound last reached the two dollar mark in September 1992.
This was just before the government withdrew from the European Exchange Rate Mechanism on Black Wednesday.