LONDON, April 18 (Xinhua) -- 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.

Brexit minister Lord Callanan said the government intended to overturn the measures at a later stage.

Political commentators say May's government could face further defeats as members of the House of Lords go line-by-line through the Brexit bill.

Keir Starmer, Labour's shadow Brexit Secretary said the passing of what was a cross-party move was an important step forward.

Starmer said: "Labour has long championed the benefits of a customs union as the only viable way to protect jobs, support manufacturing and help avoid a hard border in Northern Ireland after we leave the EU. Theresa May must now listen to the growing chorus of voices who are urging her to drop her redline on a customs union and rethink her approach."

The Independent newspaper in London said peers had inflicted an embarrassing defeat on the government after voting in favor of remaining in a customs union with the EU after Brexit. It described the move as a challenge to May's flagship Brexit bill.