European Commission President Jean-Claude Juncker has wished Vladimir Putin “every success” and congratulated him on his re-election, breaking ranks as other countries call for answers following the Salisbury poisoning.

In a letter to the Russian president Mr Juncker said he had always argued that “positive relations between the European Union and the Russian Federation are crucial to the security of our continent”.

The EU chief’s warm message comes a day after EU leaders at the European Council called on Russia to hand over details of its alleged nerve agent programme to help with the investigation into the poisoning of Sergei and Yulia Skripal, which the British government says it is certain Russia was behind.

The European Foreign Affairs Council, all 28 EU foreign ministers, issued a joint statement on Monday that said the “European Union takes extremely seriously the UK Government’s assessment that it is highly likely that the Russian Federation is responsible” for the attack.

But the statement stopped short of explicitly blaming Russia or saying that it agreed with the UK’s assessment. Russia denies any involvement and says claims it carried out the attack are “slanderous, groundless, and difficult to explain”.

Mr Juncker’s letter to Mr Putin did not mention the Salisbury incident. “Excellency, Mr President,” the Commission President wrote. “I wish to convey my congratulations on your re-election as President of the Russian Federation.

“I have always argued that positive relations between the European Union and the Russian Federation are crucial to the security of our continent. Our common objective should be to re-establish a cooperative pan-European security order.

Boris Johnson briefed leaders on the Skripal poisoning in Brussels on Monday (AP)

“I hope that you will use your fourth term in office to pursue this goal. I will always be a partner in this endeavour. I wish you every success in carrying out your high responsibilities. Yours sincerely, Jean-Claude Juncker.”

The EU institutions did not appear united on the issue, however. When asked whether Donald Tusk, European Council leader, would be sending a similar letter, a senior EU source said: “As far as I know president Tusk hasn’t sent such a letter until now. I would not be surprised if he would not send it at all.”

The letter drew immediate criticism from British MEPs. Conservative MEPs' leader Ashley Fox said:

"This is a disgraceful letter from Jean-Claude Juncker. To congratulate Vladimir Putin on his election victory without referring to the clear ballot rigging that took place is bad enough. But his failure to mention Russian's responsibility for a military nerve agent attack on innocent people in my constituency is nauseating.

"The European Commission President is appeasing a man who poses a clear threat to western security."

Skripal attack aftermath – in pictures Show all 15 1 /15 Skripal attack aftermath – in pictures Skripal attack aftermath – in pictures Scene of attack Members of the emergency services in hazard suits fix the tent over the bench where Sergei and Yulia Skripal were found unconscious on a park bench in Salisbury in March 2018. Getty Skripal attack aftermath – in pictures Victim - Sergei Skripal The retired Russian colonel and former double agent for MI6 was in a critical condition in hospital for more than two months after being exposed to novichok in Salisbury. He was given refuge in the UK after being jailed in Moscow for treason. Mr Skripal came to Britain as part of a high-profile “spy swap” in 2010 in which four men were exchanged for ten Russian "sleeper agents" in the US. In this image he is speaking to his lawyer from behind bars in Moscow in 2006. AP Skripal attack aftermath – in pictures Victim - Yulia Skripal Yulia Skripal was struck down by a novichok poison alongside her father Sergei. Facebook Skripal attack aftermath – in pictures Scene of attack A police officer stands guard outside a branch of the Italian chain restaurant Zizzi where the pair dined at before falling ill. It was boarded off whilst investigators worked on the building and later found traces of the chemical weapon within it. AFP/Getty Skripal attack aftermath – in pictures Scene of attack Large areas of central Salisbury were cordoned off by police following the discovery of the Skripals. Traces of nerve agent were also found in The Mill pub. PA Skripal attack aftermath – in pictures Victim - Nick Bailey Detective Sergeant Nick Bailey, rushed to the aid of the Russian ex-spy and his daughter who were targeted with a nerve agent. He was hospitalized after aiding them and didn't leave until three weeks after the attack. Wiltshire Police/Rex Skripal attack aftermath – in pictures Police investigation - Skripal’s home Police believe they were poisoned at home, and detectives found the highest concentration of novichok on the front door of Mr Skripal’s house. Getty Skripal attack aftermath – in pictures Theresa May visits scene of attack Britain's Prime Minister Theresa May spokes with Wiltshire Police's Chief Constable Kier Pritchard near where the Skripal's were found. Britain expelled 23 Russian diplomats over the nerve agent poisoning and suspended high-level contacts, including for the World Cup on March 14. Theresa May told parliament that Russia had failed to respond to her demand for an explanation on how a Soviet-designed chemical, Novichok, was used in Salisbury. AFP/Getty Skripal attack aftermath – in pictures Skripal days before attack Sergei Skripal days before he was exposed to Novichok, that has left him fighting for life. ITV News Skripal attack aftermath – in pictures Police investigation - military involvement British soldiers were deployed soon after the attack to help a counter-terrorism investigation into the nerve agent attack. One of the places they were asked to help out with was Skripal's home and it's surrounding. They were asked to remove a vehicle connected to the agent attack in Salisbury, from a residential street in Gillingham. AFP/Getty Skripal attack aftermath – in pictures Police investigation Personnel in protective coveralls and breathing equipment cover an ambulance with a tarpaulin at the Salisbury District Hospital. AFP/Getty Skripal attack aftermath – in pictures Police investigation The investigation extended to the grave of Sergei Skripal's son Alexander in London Road cemetery. Getty Skripal attack aftermath – in pictures Police investigation The Counter Terrorism Policing Network requested assistance from the military to remove a number of vehicles and objects from Salisbury. EPA Skripal attack aftermath – in pictures Home Secretary visits scene of attack Home Secretary Amber Rudd visited the scene of the nerve agent attack at the Maltings shopping centre on 9 March. Getty Skripal attack aftermath – in pictures Yulia Skripal speaks for the first time Yulia Skripal, speaking for the first time, said she felt lucky to have survived the nerve agent attack in Salisbury which left her fighting for life. Ms Skripal said her life had been “turned upside down” by the assassination attempt. But the Russian national added she hoped to return to her homeland one day, despite the Kremlin being blamed for the attack. Reuters

Mr Putin won 76.7 per cent of the vote with turnout of over 67 per cent of the vote. Opposition activists have pointed to irregularities in the voting process, though international observers said the poll was generally conducted efficiently.

The democratic process as a whole was "characterised by restrictions on fundamental freedoms" and "lack of genuine competition", the Organisation for Security and Co-operation in Europe however said.

"The 18 March presidential election in Russia took place in an overly controlled environment, marked by continued pressure on critical voices, while the Central Election Commission (CEC) administered the process efficiently and openly, the international observers concluded in a statement today," the OSCE said in a statement.