Brexit negotiations have been dragging for months because the British government is not focused on what really matters, a U.K. lawmaker told CNBC on Friday.

The process that will take the U.K. out of the European Union (EU) remains far from complete. The U.K. has still not outlined in precise terms how it intends to interact with the EU in the future — making issues such as the future of the Irish border undetermined.

As negotiations roll along, the final Brexit deal is becoming increasingly difficult to approve in the different European parliaments as the U.K.’s due departure next March gets closer.

“There’s been too much emphasis on the day-to-day tittle-tattle and not enough on what the long-term relationship is going to be… the issue which we really need to focus,” Lord Michael Hastings Jay, an EU Select Committee member at the House of Lords, told CNBC’s “Street Signs.”

When asked if the entire U.K. government was acting in good faith, he said: “No… I think some of them are, but not all of them. I think the prime minister is.”

The most recent spat within Theresa May’s government involved a proposal to find a temporary solution for the Irish border. After intense discussions, the U.K. government published its position on the issue Thursday, but analysts have said the EU is unlikely to accept it.

“The proposal has been reluctantly accepted by pro-Brexit members of the government, partly because of the inclusion of a vaguely-worded time-limit to the arrangement,” Danielle Haralambous, U.K. analyst at the Economist Intelligence Unit (EIU) told CNBC via email. “The big question now is whether it will be acceptable to the EU at the forthcoming summit.”

The U.K. has suggested that it should remain in the customs union — an EU agreement that allows manufacturers to move goods and parts around the continent without cost or delay — until Downing Street agrees on new terms for a new customs partnership between the U.K. and the EU.

Technically speaking, this would mean that on March 29, 2019, the U.K. will stop being a full member of the European Union, so it will no longer have voting rights in the EU, but will remain in the single market (where goods and people move freely) until December 2020. After 2020, the U.K. will only be in the customs union, so products in Northern Ireland, for instance, will have to follow the same rules as Irish goods.

The issue that the EU could have with this proposal is that the U.K. didn’t specify until when this “backstop solution” would be in place.

“We expect the EU to challenge various aspects of the backstop and push for another iteration of it, to be agreed later this year,” Haralambous from the EIU said.

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It is expected that many EU leaders will be reluctant to accept the proposal given this lack of clarity about its duration.

Brexit will be discussed at a European summit later this month in Brussels.

A European official told CNBC earlier this week that Brexit had become “stuck” in the U.K. Officials in Brussels have been complaining that, until the latest proposal sent from the U.K., they had nothing new to work on ahead of the summit.

Although the proposal is unlikely to be fully accepted in Brussels, officials there can now prepare a position to put forward to Prime Minister May.