Sir Keir, accompanied by Shadow Levelling up Secretary Lisa Nandy, spent several hours at the factory in Altham as part of a three day tour of the country in which he will set out Labour' s plans to build prosperity across the nation.
Speaking to the Burnley Express, Sir Keir said: "The Government's been in power for 12 years now. Coming to a place like Burnley and saying they're finally getting round to putting some money in is insulting frankly.
"We need a government that matches the ambition of people in Burnley and surrounding areas. We're her at What More, a manufacturing company that pulls together skills from Burnley College, the apprentices here, the investment that's needed.
"We the Labour Party have got a package of £28 billion a year on the next generarion of jobs. We want a buy, make and sell policy in Britain which means jobs will be local, and we want to deal with business rates and making our high streets thrive again. Levelling up will only happen if the scale of the plan matches the ambition of people in Burnley and other areas."
Sir Keir was also asked what Labour could do to win back the so-called 'Red Wall' seats across the North West that it lost to the Tories in the last general election, including Burnley where a Conservative was elected for the first time in generations.
"We know that we've got to earn every vote," he said.
"It was really important after the last election that we change the Labour Party and that's what we've done. We've turned the Labour Party inside out and made sure that what we want to happen matches what local people want to happen - for their town to be a thriving place and somewhere where they don't have to get out to get on. We've listened hard to that."
Sir Keir and Lisa Nandy will visit Burnley College later today where they will chat with students about what they want to see.