That is the message from the General Secretary of  the Independent Workers' Union of Great Britain.  His point is that many of these so called self employed contractors are, in reality, workers and are entitled to some employment rights such as the right to receive paid holiday and the national minimum wage.

HMRC are responsible for enforcing the NMW and can make employers pay arrears and fines and he suggests it should do much more to help workers enforce their rights.  

The director of labour market enforcement, David Metcalf is reviewing how the government can assist workers to enforce their rights and to improve the effectiveness of enforcement agencies such as HMRC. In a letter sent to stakeholders last week, Mr Metcalf argued that one aspect of improving enforcement is building on the deterrence effect: “The threat of investigation and enforcement must act as a deterrent to employers to proactively spur change in compliance more widely than only those directly inspected. This relies on both the perceived probability of investigation and the expected level of penalty.” 

That would certainly help.  However, lowering or abolishing Employment Tribunal fees would probably be of greater benefit.  Claims have fallen dramatically since fees were introduced and, despite what many consider to be compelling evidence that this has resulted in many people with genuine claims being denied access to justice, the government remains committed to retaining fees.