I recently saw a good answer to that question on why taxes are high but public services are poor.
Consider two different people, person A and person B. Person A buys a decent house by taking out a mortgage on it. His monthly expenditure consists of paying the mortgage, the bills, food, and because the house is in good condition, a minimal amount on maintenance. At the end of each month he has some disposable income to spend on luxuries such as a new car or to put it towards home improvements.
Person B buys a house with the same size mortgage that is in need of improvement, in other words there are problems with the roof, rotting window frames, the plaster is coming off the walls, there are damp problems, and the electrics need rewiring. His monthly expenditure consists of paying the mortgage, the bills, food, and trying to save every last penny to hire contractors to gradually fix the problems, step by step. Fixing these issues consumes all of his remaining monthly income after the essentials have been paid for and he has none left over to make other improvements or for luxuries.
Person B is an analogy of the incoming Labour government and their house is an analogy of the UK after the previous conservative government. Once it was apparent they were getting kicked out at the election they ran public services into the ground and built up a £20 bn debt, knowing that the incoming Labour government would have a huge mountain to climb to sort it out, and would not be able to do so without raising taxes. Once Labour have raised taxes, they can sit there in opposition and say "Look, Labour have raised taxes as soon as they got in, you can't trust them, we didn't raise taxes, vote for us next time, we can run the economy better".