Chancellor Philip Hammond has been urged to do more for family firms in this week's Budget.
The Institute for Family Business (IFB) said the sector needs stability and clarity from the Government.
With family businesses generating a quarter of GDP, employing 12 million people, and paying £133 billion in tax, the IFB said Mr Hammond needed to address the concerns of such firms.
The IFB is calling for the Government to maintain Business Property Relief in full, and extend the Enterprise Investment Scheme to support growth.
IFB executive director Elizabeth Bagger said: "During periods of upheaval, family businesses provide resilience in the economy.
"In the wake of the EU referendum, family businesses need stability and clarity and the confidence to make investments which will deliver growth for the long term.
"That's why we are calling on the Chancellor to take action to support this vital section of the business community, which contributes a quarter of economic growth and employs more than 12 million people.
"As well as making it easier for family businesses to be transferred between generations, the Government should ensure that the tax system encourages succession planning."