LONDON -- The British government's Brexit department Wednesday night brushed off what was their first major defeat in the unelected House of Lords.

Peers in British Parliament's upper chamber voted by 348 to 225 in favor of a call requiring government ministers to report on steps to negotiate a continued customs union with the European Union.

The House of Lords is currently debating Prime Minister Theresa May's European Union withdrawal bill, the legislation needed to end Britain's membership of the bloc after more than 40 years.

The government has insisted that leaving the EU single market as well as the customs union are a key part of its Brexit strategy.

A spokesperson for Brexit department, officially called the Department for Exiting the European Union (DExEU), later issued an official statement in response to the vote in the House of Lords.

The spokesperson said: "We are disappointed that Parliament has voted for this amendment. The fundamental purpose of this (Brexit) Bill is to prepare our statute book for exit day, it is not about the terms of our exit.

"This amendment does not commit the UK to remaining in a Customs Union with the EU, it requires us to make a statement in Parliament explaining the steps we've taken.

"Our policy on this subject is very clear. We are leaving the Customs Union and will establish a new and ambitious customs arrangement with the EU while forging new trade relationships with our partners around the world."

The move in the House of Lords was backed by Lord Patten, a former EU commissioners, and the last British governor of Hong Kong before it was handed back to China.

Patten said Britain would be worse off unless current arrangements with the EU continued.