Boris Johnson has urged the government to provide long range missiles to Ukraine to allow them to "take out" Russian launch sites.
Johnson spoke to MPs on Monday and pleaded for defence secretary Ben Wallace to pledge more support for the Ukrainian army.
Equipment should include drones, anti-aircraft missiles, planes, armoured cars and tanks, and long-range systems such as ATACMS, he said.
The former PM said: "The House will know that supplies of British, American and other Western equipment have been absolutely vital in helping our Ukrainian friends to protect themselves against continuing and merciless Russian attacks, and I thank him and the government for all that they have done and continue to do.
“Does he agree with me that we and our allies must help our Ukrainian friends not just to take out the drones and missiles, and that means supplying them with anti-aircraft systems and fixed-wing aircraft to help shoot them down, but also to take out the launch sites of those missiles and drones by supplying the Ukrainians with the use of longer-range missile systems such as ATACMS because that is the way truly to protect our Ukrainian friends and to bring the war to an end as soon as possible?”
Downing Street indicated the UK is not planning to provide long-range missiles to Ukraine.
Rishi Sunak’s official spokesman said: “You will know that the military equipment that we provide to Ukraine is for use in Ukraine to enable it to defend itself against the illegal invasion.
“I’m not aware of any plans to alter that approach but obviously we keep these things under review.”
Wallace replied in parliament: “Without my right honourable friend’s support to me and Ukraine, none of this would have been possible and I want to place on record my great appreciation for his support through that process.
"He’s absolutely right that the Russians are taking advantage of the short-range capability of the Ukrainian armed forces by using these Iranian kamikaze drones.
“As we see against all the rules of law, including the Geneva Conventions, the mass targeting of civilian critical infrastructure is not only a war crime, but is a war crime that we must see does not go unpunished.”
Wallace said he constantly reviews the “weapon systems we could provide”, adding: “Should the Russians continue to target civilian areas and try and break those Geneva Conventions, then I will be open-minded to seeing what we do next.”
If followed, the move would mark an escalation of intervention by outside sources.
Western allies are yet to have provided artillery to such an extent, however Johnson is not the first European politician to call for a higher grade of weaponry.
In June, Lithuanian Prime Minister Ingrida Šimonytė called for long range weapons to be provided by either the United States or a European ally.
“The Ukrainians need this sort of weapon,” she said, adding that either US-made ATACMS or a European equivalent would do.
Last week pictures emerged of piles of thousands of Russian missiles collected by Ukrainian soldiers in the city of Kharkiv, showing the scale of bombardment on the city by the Russian army.
Retired US Army major John Spencer posted what he described as the "insane" photo showing two police officers looking at a fragment pile of Russian rockets that hit Ukraine's second largest city of Kharkiv.
Other images showed more piles of missiles and shells collected by 'sapper' soldiers after Ukraine regained control of Kharkiv in September.
Spencer used the images to repeat his own plea for long range missiles to be sent to Ukraine.
"I still strongly believe the U.S. should provide Ukraine [with] ATACMS, Grey Eagle, Patriot missile systems, and more," he said.
"It will greatly assist in ending Russia's illegal war quicker.
"Stop appeasing Putin. The longer the war continues, the risks of escalation/spill-over actually increase."