Germany fears Britain may pull out of a key intelligence-sharing programme in May next year, a move that it says would create a “moment of weakness” in the fight against terrorism and jeopardise security across the EU.

As the continent remains on alert for terrorist attacks, Berlin is understood to view intelligence as Britain’s primary contribution to European collaboration, and fears it could use future cooperation as a bargaining chip in Brexit negotiations.

According to documents seen by the Guardian, Germany is already lobbying the British government to renew its role in Europe’s law enforcement agency, Europol, before its current collaboration runs out on 1 May 2017.

In a response to a parliamentary question submitted by Germany’s Left party, Angela Merkel’s government confirmed that it believed the European commission should encourage the UK to remain in Europol.

Doing so was in Britain’s interest, the document produced by the German interior ministry said, because “collaborating and sharing information via Europol can help the UK prevent and fight terrorism and serious crime”.

After a series of attempted terrorist attacks over the summer and a politically charged debate about the risks of Merkel’s stance during the refugee crisis, German politicians in particular are concerned that Britain could use its large intelligence capacities as a bargaining chip.

“Recent attacks and arrests of suspected terrorists have shown that a close collaboration between international security agencies is indispensable,” said Stephan Mayer, the interior policy spokesperson of Merkel’s CDU/CSU party group. “Even after a possible Brexit, the fight against terrorism will remain an enormous challenge for European states; and this naturally applies to Europol’s work too.

“All those responsible have to guarantee that this cooperation continues successfully and without friction in spite of a Brexit. The international fight against Islamic extremism and terrorism cannot afford a moment of weakness.”

European governments and Brussels officials have been emphasising in public that there can be no pre-negotiations with Britain, however informal, until May officially informs the EU of its intention to leave by triggering article 50. Before October’s European council meeting in Brussels, German government officials vehemently denied that security cooperation would form part of the discussions at the summit.

But the EU’s united front has been undermined by some inconvenient timetabling. On 1 May 2017, a month after the deadline May has given herself for triggering article 50, the European Union will adopt a regulation that expands the role of the European parliament and national EU legislatures in supervising Europol’s operations.

On Friday, May told EU officials that she would stick to her deadline in spite of the high court’s decision that her government must get parliamentary approval to trigger article 50. Some MPs have suggested the need to draft new legislation may further squeeze the planned timetable.

The UK is not part of the border-free Schengen zone and has an opt-in into Europol, which will automatically expire as soon as the new rules come into effect. By dropping out of Europol, the UK would automatically be shut out of a number of other agencies and intelligence cooperation programmes, such as the Schengen-wide information system SIS II.

A Home Office spokesman pointed to recent comments made by Brandon Lewis, the policing minister, who said no decision had yet been taken on Europol. “The decision on whether we opt into the further Europol regulations will be announced to parliament shortly. We will take that decision very soon; we are giving good consideration to where we are on that and will make an announcement to parliament in due course,” he said.

Last week Lewis confirmed in a letter that the UK would press ahead with an opt-in to the Prüm convention, an EU-wide system for sharing DNA samples, fingerprints and vehicle registration.

A report (pdf) by the German parliament’s academic service recently raised alarm over the hole that Brexit could leave in Europe’s security network, and pointed out that the UK would no longer have direct access to Europol’s databases.

Europol, which is based in The Hague, started operations in 1999 and is funded through the EU budget. It has a British director, Rob Wainwright, and according to a spokesperson, 40% of its cases have a “British dimension”.

German government officials told the Guardian that there was still hope in Berlin that as a former home secretary, May would appreciate the value of cooperating on counter-terrorism measures. In a private speech at Goldman Sachs before the EU referendum, recently leaked to the Guardian, May expressly argued that British security was best served by remaining in Europe.

The German Left party MP Andrej Hunko, who submitted the query to the government, said that although the UK had been one of the main drivers behind Europol’s engagement in covert intelligence networking, Britain opting out of the agency could potentially give rise to even more informal and less democratically accountable forms of information-sharing.

“After Brexit, the strengthening of informal structures such as the police working group on terrorism and the Club de Berne could become a major cause for concern”, Hunko said. “These institutions don’t form part of the European Union and are thus harder to control by either delegates in the European parliament or our national parliaments, with national governments remaining as secretive about such networks as they can.”

From the position of the German Left party, Hunko said, “the question of whether British police should remain part of Europol is therefore a choice between the devil and the deep blue sea”.