The following chart is taken from How Should Britain’s Government Spending and Tax Burdens be Measured? by David B Smith, IEA, Jun 2009:
It seems to show an upper limit to the tax which can be extracted from the economy: about 40% of GDP. Further, there has been little change in taxation either way since the 70s, from this point of view.
So, is there any reason to believe taxes can usefully be raised further?
Not from this evidence. It seems that government spending in excess of 40% of GDP must inevitably be covered by debt and debasement. More in due course.