How to stop condensation

Our bathroom is becoming a mouldy mess due to a pipe at the right of the window. All was well in the summer and as soon as the cold weather hit the condensation started on the pipe (it’s wet) and the mould started to spread around the window area. How is best to tackle this. We have looked at various options (mould remediation, humidifier, extract fan). But they are all expensive and want to make sure we are making the right decision in that the mould will not come back. We really just need this pipe to stop producing condensation. Advice greatly appreciated - thanks.