Apparently Burnham wrote a letter to ministers, in which he said this:

I am clear in my conviction that the Brexit deal negotiated by the Conservative government was not good enough for Britain… It has led to a decade of low growth, burdened businesses with more red tape and weakened our ability to control immigration. It is a harder Brexit than was promised at the EU referendum.

…we will need to consider the UK’s long-term relationship with the EU as part of our 10-year plan. I will set out the next steps for this process around the [UK-EU] summit.

Hopefully that summit brings some good news (i.e. closer relations between the UK and EU).