The European Parliament will withdraw access to Amazon's lobbyists amid a bitter row between EU lawmakers and the online retail giant over labour issues, a parliamentary source said Wednesday.

Amazon said it was "disappointed" by the decision and defended its willingness to work with lawmakers, stressing that it had engaged "constructively".

This is only the second such ban the parliament has issued after it barred lobbyists from US agro-chemicals giant Monsanto in 2017.

A spat between the parliament's employment committee and Amazon has been escalating in recent weeks, with both sides accusing the other of bad faith.

The parliamentary source confirmed reports that an internal body in the parliament took the decision to ban the lobbyists but would not give further information.

It is not clear when the ban comes into effect and what Amazon could do to gain access to the parliament premises in Brussels again. Amazon had 14 badges.

Dutch lawmaker Agnes Jongerius, a member of the parliament's employment committee, welcomed the decision as she accused Amazon of denying access to EU lawmakers seeking to visit company warehouses in Germany and Poland.

"Why should we grant access for a company who doesn't welcome us in their territory?" she told journalists Tuesday.

The committee has been looking into Amazon, particularly regarding workers' pay and conditions as well as concerns surrounding the company's stance on unionisation.

Amazon said it was "inaccurate" to suggest the company withdrew or cancelled visits.

"The committee proposed specific dates that we could not accommodate, as they fell during our busiest time of year -- no date was ever agreed upon," a spokesperson said.

Jongerius noted, however, that the badges' withdrawal did not mean Amazon lobbyists or employees could not access the parliament on a case-by-case basis.

"We're not banning them from the Parliament full stop but just 14 people walking around the premises while they don't want to answer legitimate questions about their working conditions," she said.

Amazon said the company had always shown willingness to engage in dialogue.

"We're confident that we've engaged in a constructive spirit, unlike some critics who seem more concerned with scoring a win than progressing the understanding of important issues," the company retorted in a blog post.

An Amazon spokesperson said an "invitation still stands" to visit its facilities.

Amazon has spent 18.8 million euros ($20 million) on lobbying European institutions, according to campaign group Corporate Europe Observatory.

European trade unions and civil society organisations welcomed the move that came after more than 30 of them called on parliament to take this action.

"The European Parliament has drawn a clear red line: Amazon's anti-democratic behaviour won't be tolerated - whether that's towards trade unions or parliaments," said Oliver Roethig, of the European services workers' union UNI.

Amazon has more than 150,000 employees in the European Union.