GST may have to rise if the financial crisis worsens and politicians stick with their big election promises, warns a tax specialist.
PricewaterhouseCoopers chairman John Shewan says he believes it will be an inevitable consequence of loose fiscal policies.
The last Treasury update showed a $10.2 billion deterioration in government finances and forecast a decade of deficits.
Mr Shewan told Nine to Noon that increasing GST to 15% from 12.5% could generate an extra $2 billion in revenue a year.
He said politicians will have to look seriously at the option if they face rising debt reaching unacceptable levels.
Mr Shewan thinks crunch time may come in December after any coalition talks.
He also said the current tax structure - whereby 15% of the population pays more than 60% of total income tax - is not sustainable and tax cuts should go ahead.
Health advocates are warning that families and children could suffer if GST is increased.
Public Health Association executive director Gay Keating says increasing GST would make it harder for families who are already living in severe deprivation to afford food and healthcare.
Dr Keating says people who are unhealthy are going to cost the healthcare system more in the long run.
She says the association would like the idea of removing GST from healthy foods to be explored.
Both National Party leader John Key and deputy Labour leader Michael Cullen have said they do not support the idea of raising GST.
GST, or Goods and Services Tax, is added to the price of taxable goods and services and was introduced by the Lange government in 1986. The rate was initially 10%, but was raised to 12.5% in 1989.
