National is sitting on a low 38 per cent according to a secret Labour-run poll.

Three years of Labour's internal polling data leaked to NewsHub from a non-government source shows National at 38 per cent - the same score it had during the Jamie-Lee Ross drama.

It also shows how other events also negatively affected public opinion of the right wing party with it also dropping below 40 when leader Simon Bridge's expenses were leaked revealing he had spent more than $100,000 on limos and hotels during a three-month period last year.

The data, according to NewsHub, also shows Labour's highs and lows in the last three years, with it dropping to a record low of 23 per cent in July 2017 under Andrew Little's leadership before jumping to 37 per cent when Jacinda Ardern took over the reins.

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Labour made even better headway when Simon Bridges took over National's leadership in February last year.

The birth of Ardern's baby, Neve in June 2018 saw Labour's ratings spike again.

Labour also received a record 47 per cent following its response to the Christchurch terror attacks earlier this year, NewsHub reported.

But it hasn't been all smooth sailing for the Government with its polling taking a hit over problems with KiwiBuild.