Britain will double the numbers of Ukrainian troops it is training, it has been announced, as Russian backed separatists launched their biggest assault in six months against government forces.

Defence Secretary Michael Fallon declared that the move was imperative as the violence in the east of the country, orchestrated by Vladimir Putin, “shows no sign of ending anytime soon”. “Russian inspired terrorism”, he maintains, has ensured that the conflict was “certainly not frozen” but one which is “red hot” with Ukraine’s borders “under threat.”

The training programme will raise the total of Ukrainian forces being trained from a thousand to two thousand by the end of the year. Mr Fallon, during a visit to Ukraine, also stated that he is open to request from Kiev for additional trainers; their numbers have already gone up from an initial deployment of 35 earlier this year to 75, operating in six locations.

The countries providing training for the Ukrainian forces – the US, UK, Canada, Poland and Lithuania – will be meeting in the autumn, with London the possible venue, to plan steps to aid the beleaguered government of Ukrainian president Petro Poroshenko.

Ukraine crisis: A timeline of the conflict Show all 23 1 /23 Ukraine crisis: A timeline of the conflict Ukraine crisis: A timeline of the conflict 30 November 2013 Public support grows for the “Euromaidan” anti-government protesters in Kiev demonstrating against Yanukovych’s refusal to sign the EU Association Agreement as images of them injured by police crackdown spread. EPA Ukraine crisis: A timeline of the conflict 20 February 2014 Kiev sees its worst day of violence for almost 70 years as at least 88 people are killed in 48 hours, with uniformed snipers shooting at protesters from rooftops. AFP/Getty Images Ukraine crisis: A timeline of the conflict 22 February 2014 Yanukovych flees the country after protest leaders and politicians agree to form a new government and hold elections. The imprisoned former Prime Minister, Yulia Tymoshenko, is freed from prison and protesters take control of Presidential administration buildings, including Mr Yanukovych's residence. Genya Savilov/AFP/Getty Imageses Ukraine crisis: A timeline of the conflict 27 February 2014 Pro-Russian militias seize government buildings in Crimea and the new Ukrainian government vows to prevent the country breaking up as the Crimean Parliament sets a referendum on secession from Ukraine in May. Sean Gallup/Getty Images Ukraine crisis: A timeline of the conflict 16 March 2014 Crimea votes overwhelmingly to secede from Ukraine and join Russia in a ballot condemned by the US and Europe as illegal. Russian troops had moved into the peninsula weeks before after pro-Russian separatists occupied buildings. EPA Ukraine crisis: A timeline of the conflict 6 April 2014 Pro-Russian rebels seize government buildings in the eastern cities of Donetsk, Luhansk and Kharkiv, calling for a referendum on independence and claiming independent republic. Ukraine authorities regain control of Kharkiv buildings on 8 April after launching an “anti-terror operation” but the rest remain out of their control. EPA/PHOTOMIG Ukraine crisis: A timeline of the conflict 7 June 2014 Petro Poroshenko is sworn in as Ukraine's president, calling on separatists to lay down their arms and end the fighting and later orders the creation of humanitarian corridors, since violated, to allow civilians to flee war zones. Getty Images Ukraine crisis: A timeline of the conflict 27 June 2014 The EU signs an association agreement with Ukraine, along with Georgia and Moldova, eight months after protests over the abandonment of the deal sparked the crisis. LOUISA GOULIAMAKI/AFP/Getty Images Ukraine crisis: A timeline of the conflict 17 July 2014 Malaysian Airlines flight MH17 is shot down over eastern Ukraine, killing all 298 people on board. Ukrainian intelligence officials claim it was hit by rebels using a Buk surface-to-air launcher in an apparent accident. Ukraine crisis: A timeline of the conflict 22 August 2014 A Russian aid convoy of more than 100 lorries enters eastern Ukraine and makes drop in rebel-controlled Luhansk without Government permission, sparking allegations of a “direct violation of international law”. Reuters/Alexander Demianchuk Ukraine crisis: A timeline of the conflict 29 August 2014 Nato releases satellite images appearing to show Russian soldiers, artillery and armoured vehicles engaged in military operations in eastern Ukraine. Nato Ukraine crisis: A timeline of the conflict 8 September 2014 Russia warns that it could block flights through its airspace if the EU goes ahead with new sanctions over the ongoing crisis and conflict EPA Ukraine crisis: A timeline of the conflict 17 September 2014 Despite the cease-fire and a law passed by the Ukrainian parliament on Tuesday granting greater autonomy to rebel-held parts of the east, civilian casualties continued to rise, adding to the estimated 3,000 people killed Reuters Ukraine crisis: A timeline of the conflict 20 October 2014 A 'tactical missile' explosion at a factory sends blast wave across rebel-held cityof Donetsk YouTube Ukraine crisis: A timeline of the conflict 16 November 2014 The fragile ceasefire gives way to an increased wave of military activity as artillery fire continues to rock the eastern Ukraine's pro-Russian rebel bastion of Donetsk Getty Ukraine crisis: A timeline of the conflict 26 December 2014 A new round of ceasefire talks, scheduled on neutral ground in the Belariusian capital Minsk, are called off AFP/Getty Ukraine crisis: A timeline of the conflict 12 January 2015 Soldiers in Debaltseve were forced to prepare heavy defences around the city; despite a brief respite to the fighting in eastern Ukraine, hostilities in Donetsk resumed at a level not seen since September 2014 AFP/Getty Ukraine crisis: A timeline of the conflict 21 January 2015 13 people are killed during shelling of bus in the rebel-held city of Donetsk Reuters Ukraine crisis: A timeline of the conflict 24 January 2015 Ten people were killed after pro-Russian separatists bombarded the east Ukrainian port city of Mariupol AP Ukraine crisis: A timeline of the conflict 2 February 2015 There was a dangerous shift in tempo as rebels bolstered troop numbers against government forces AFP/Getty Ukraine crisis: A timeline of the conflict 11 February 2015 European leaders meet in Minsk and agree on a ceasefire in eastern Ukraine beginning on February 14. From left to right: Belarus President Alexander Lukashenko, Russian President Vladimir Putin, German Chancellor Angela Merkel, France's President Francois Hollande and Ukrainian President Petro Poroshenko. MAXIM MALINOVSKY | AFP | Getty Images Ukraine crisis: A timeline of the conflict 13 February 2015 Pro-Russian rebels in the city of Gorlivka, in the Donetsk region, fire missiles at Ukrainian forces in Debaltseve. Fighting continued in Debaltseve for a number of days after the Minsk ceasefire began. ANDREY BORODULIN | AFP | Getty Images Ukraine crisis: A timeline of the conflict 18 February 2015 Ukrainian soldiers repair the bullet-shattered windshield of their truck as their withdraw from the strategic town of Debaltseve. Following intense shelling from pro-Russian rebels, Ukrainian forces began to leave the town in the early hours of February 18. Brendan Hoffman | Getty Images

Mr Fallon’s visit came on the day that Kiev accused the separatists of carrying out an offensive with 400 fighters, heavy artillery and tanks around the village of Starohnativka, 30 miles south of the port of Mariupol, a key strategic point which has been the focus of sustained fighting.

Control of the port would allow a land corridor to be formed from rebel controlled territories to Crimea which the Kremlin annexed last year following the uprising which saw the fall of Russian backed president Viktor Yanukovych.

“This brazen attack by the occupiers took place against a background of an escalating situation in east Ukraine,“ said military spokesman Andriy Lysenko of the Kiev government. The separatist attack, he added, was the heaviest since a battle for the town of Debaltseve in February.

A senior separatist commander Eduard Basurin denied the rebels had attacked government troops and accused the Ukrainian government of instigating the upsurge in violence.

Critics have claimed that sending the training team was an ill-thought reaction by David Cameron who had faced severe criticism for Britain having no voice in what was going on in the Ukraine. The Minsk II agreement which resulted in a ceasefire was brokered by German Chancellor Angela Merkel and Francois Hollande, the French President, without any involvement by London.

Mr Fallon dismissed claims that the UK risked “mission creep” and that Western entanglement in the war will provoke President Putin and jeopardise the peace process.

“This is not provocative. This is all designed to help the Ukrainian forces better defend themselves and to save lives. All of it is being well away from the conflict zone” he insisted. “We were dealing with infantry, intelligence, medical, logistics.

“ We are going to be adding training in ground threat awareness, train them in how to recognise mines and IEDs, training them in urban operations, how to defend themselves better in urban environments, in engineering expertise, how to fortify themselves better in the field.. “

The continuing Russian threat must not be underestimated, he said: “While they retain heavy weapons in the Donbass, and significant numbers of troops, you can’t rule out this continuing threat to Ukraine’s eastern border.”

There have been rising concern that right-wing militias, some of whose members are openly neo-Nazis, which had been fighting against the rebels have become highly influential in the Ukrainian security establishment. The Defence Secretary maintained that the Kiev government has carried out vetting to ensure that none of those being trained by the British are extremists. “ We are going to make sure that is the case”, he said.