Caltex service stations will stop accepting AA Smartfuel discount cards from August 1.

In a letter sent out to subscribers this week, AA Smartfuel managing director Scott Fitchett said the organisation had ended its partnership with Caltex "due to competitive commercial reasons".

Fitchett added that AA Smartfuel would continue its partnership BP and announce new fuel partners by the end of July, taking the overall reach of the loyalty programme to 300 sites nationwide.

The discounts earned through the programme amounted to a record $132 million last year.

In addition to Caltex, petrol stations Z Energy, Gull, Mobil and Waitomo are also not involved in the programme.

New Zealand fuel prices have edged upwards over the last few months - a trend that continued in May.

According to the AA Motoring blog, the price of 91 Octane has risen from $2.06 per litre in January to $2.28 per litre by end of May.

While this is still well below last September's highs when fuel crept over $2.40 per litre, there are concerns over further increases due to another tax.

In late May, the Herald reported the Government has passed under urgency a law implementing the second of three annual increases in fuel tax - adding another 3.5 cents per litre to the cost.