Boris Johnson is planning a trip to Ukraine to visit President Volodymyr Zelenskiy despite concern among senior Conservatives that the trip could undermine the authority of Rishi Sunak. The former prime minster has told friends he intends to travel to Kyiv in the coming months to show his public support for the country against its Russian aggressors. Ukrainian sources also said Johnson “had an intention” to travel to Kyiv but they had “no concrete information” yet on dates. They said Zelenskiy and the former prime minister regarded each other as “friends”. Johnson had pitched himself as a strong supporter of Zelenskiy during his time in office, pushing international allies to provide more support in the early days of the war. The UK has provided substantial economic, humanitarian and defensive military assistance to Ukraine, committing to spend at least £2.3bn in 2023. A popular figure in Ukraine, Johnson called his counterpart in Kviv frequently while at No 10, although as his premiership unravelled he was accused of using the calls as a distraction whenever he faced another crisis. It is understood Downing Street was not aware of the planned trip, although government insiders said they were relaxed about Sunak’s predecessor-but-one representing the UK in this way. A spokesperson for Johnson declined to comment. Johnson, as a former premier, will receive taxpayer-funded security protection on foreign trips based on an assessment of the potential threat. The Ukrainians are also expected to provide security, as they would with all visiting foreign dignitaries. However, Johnson’s plan to burnish his post-Downing Street credentials on the world stage has been met with some consternation at Westminster, where Sunak’s allies accused his predecessor of undermining the prime minister’s authority. Tobias Ellwood, the chair of the Commons defence select committee and a former army officer, warned Johnson should “not interfere” with the official relationship between the two countries. He said: “Any senior visitor from the west will of course be welcomed by Kyiv, not least a former premier who pioneered UK’s military assistance to Ukraine from the start. “But Russia’s ability to endure hardship is greater than the west. Putin is retooling his industries to help the war effort and mobilising further thousands for a major spring offensive. “This conflict is far from over. Boris should leave no doubt that he fully supports No 10 and his visit should not interfere with the messaging or the official lines of communication between London and Kyiv.” One minister, an ally of Sunak, suggested Johnson was trying to have his “Churchill moment”. They added: “This is as much about how Boris views his role on the world stage as it is about backing Ukraine. The situation there remains extremely fragile so he needs to be careful not to compromise Rishi’s relationship with Zelenskiy.” Another Tory MP suggested Johnson’s trip to Kyiv would make him a more attractive proposition on the international speaking circuit. Over the course of his first four months out of office, he made more than £1m delivering four speeches. They said: “It’s all about brand Boris. It’s a marketing ploy to make him more relevant and get him more speaking gigs in the US. He’ll be a bigger draw if he’s just been to Ukraine.” Only a handful of British politicians have travelled to Ukraine since the Russian president, Vladimir Putin, ordered troops to invade last February, including Johnson, Sunak and defence secretary Ben Wallace. The trip will be the fourth time the former prime minister has travelled to Kyiv – having first visited in April soon after Russian troops abandoned their attempt to seize the capital. He went to Ukraine for a second surprise visit in June and returned again in August for the country’s independence day. Sunak, whose first international call after taking office was to Zelenskiy, made a surprise visit to Kyiv in November, where he pledged UK support for Ukraine in the fight against Russia would remain steadfast. Days before Johnson pulled out of the Tory leadership contest against Sunak in October, the Ukrainian government’s official Twitter page posted a meme based on the Netflix show Better Call Saul, with a picture of the former prime minister’s face and the words “Better Call Boris”. It was deleted soon after. Truss had intended to travel to Ukraine early on, but in the end her premiership was too short-lived to organise a visit, especially after the period of national mourning after the Queen’s death, her trip to New York for the UN general assembly, the disastrous mini-budget and party conference season.