The Labour leader has warned the UK should avoid turning itself into a tax haven in the wake of Brexit, reports the Mirror.
Jeremy Corbyn was in Brussels to make sure the "negotiations get on track" as Mrs May attended the EU summit in the Belgian capital.
The Labour leader, who had an hour-long meeting with the EU's chief negotiator, Michel Barnier,gave a speech to European socialists about the future of the left.
Mr Corbyn told reporters he wanted to make sure the UK did not turn itself into a tax haven which would threaten jobs.
He said: "We are here to make sure the negotiations get on track, that we defend jobs in Britain and that we make sure there is a trade access in Europe in future, we have to defend jobs in Britain and we have to have a trade relationship with Europe, we don't need to be threatening Euope with an offshore tax haven."
He also met with the prime ministers of Sweden and Italy, a tour of the parliament and a meeting with the president of the European Parliament.
Ahead of his speech the Labour leader also warned that a no-deal Brexit would be "catastrophic" for manufacturing industry jobs and would create problems throughout the economy.
He said: "don't want to see that I want to see an agreement being reached, that is why we're here, that we why are doing our best to ensure an agreement can be reached and I believe it can be reached.
"We have to recognise the seriousness of the situation and the chaos in which our government is operating in at the present time and it's a chaos of their own making."
In his address to the European socialists the Labour leader warned that the left needed to come forward with a "radical alternative" to the "failed" policies of austerity if they were to counter the rise of the extreme right.
He said that for too long the most prominent voices on the left had looked out of touch and "too willing to defend the status quo" while right wing nationalists reaped the benefits of a "broken" system.
"From Donald Trump in the United States, Marine Le Pen in France and Ukip in Britain, to the worrying rise of the far right elsewhere in Europe, including most recently in Austria, our broken system has provided fertile ground for the growth of nationalist and xenophobic politics," he said.
"Unless we offer hope for a more equitable and prosperous future, we will effectively be clearing the path for the extreme right to make even more far-reaching inroads into our communities, and their message of fear and division to become the political mainstream in our political discourse."