The party's Brexit secretary criticised the agreement and said Labour could not back the deal during a vote in parliament.
Ms May revealed that her cabinet had reached a collective decision on the draft Brexit deal that had been struck by negotiators this week.
Now, Labour's Brexit secretary has confirmed that the party would be voting against Ms May's agreement.
Sir Keir said the deal was "not good enough for manufacturing and services" and also did not have the necessary safeguards to protect rights.
"We said we would judge the deal once we had seen it. We have now read and analysed the 500 or so pages. It is a miserable failure of negotiation,” Sir Keir said on Sky News.
“There is huge detail on issues like the backstop that the government says it does not intend to use and on then on the question on what you intend to use and the future relationship there is seven pages.
“…We will vote against this deal because it does not meet our tests. I don’t think anybody would sign up to a document without knowing where it was heading.”
Sir Keir added that he believed the agreement would make striking future trade deals more difficult.
The comments come as it was announced that MPs could be given the opportunity to table amendments on the governments' motion.
Sources who spoke with Ms May suggested they believed that ministers were heading towards agreeing that MPs will be able to vote on amendments before voting on the deal itself.
The development raises the prospect that MPs may only back the deal if certain conditions are met - for example, that there is a Final Say referendum.
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