Coca-Cola has been accused of using legal manoeuvres to delay an official investigation into a misleading advertising campaign in Mexico by accusing the government agency of acting unconstitutionally.

Campaigners say that a multimedia publicity campaign launched at the beginning of 2015 misled consumers by suggesting that Sidral Mundet – an apple-flavoured drink which contains 60 grams of sugar in each 600ml bottle – was made from apples.

Adverts bearing the slogans “with apple juice” and “with pasteurized juice” accompanied by images of juicy apple slices were plastered across billboards, bus stops and delivery vans.

More than 70 videos suggesting the drink is made from fresh apples were also posted on YouTube. In one video, a whole red apple emerges from a flower pot after Sidral is poured in. In another, the drink is made by mixing an apple in a cocktail shaker.

Sidral was launched in Mexico in 1902, and bought by Coca-Cola in 2002. It contains 1% of “juice from concentrate” – which is classified an added sugar by the Food and Drug Administration (FDA).

In February, the campaign group Consumer Power reported the company to federal authorities, accusing Coca-Cola of intentionally misleading consumers about the content and benefits of Sidral. The group also claimed that the use of the term “pasteurized” is also disingenuous as it normally applies to fruit juices, not sodas.

The federal prosecutor’s office for consumer rights (Profeco) asked Coca-Cola to clarify how much apple juice and apple flavour the drink contains, and explain its use of the word pasteurized.

In response, the company launched a legal challenge in March claiming that its constitutional right to a fair trial had been violated, and arguing that the country’s federal consumer rights law is unconstitutional.

Coca-Cola also claimed that the complaint was directed at the wrong party, as its publicity and labeling is run by a subsidiary, Propimex.

The soft drinks giant convinced the judge to suspend the complaint against Sidral until its petition was resolved.

“Coca-Cola’s primary objective was to delay the process so that it could continue with its campaign,” said Javier Zuñiga, lawyer with Consumer Power.

“The case is an abuse of the constitutional claim system as the company was simply asked to clarify basic details. It bought Coke time, and consumers are left with the idea that Sidral is a healthier option when it should be seen as exactly the same as every other sugary fizzy drink,” Zuñiga told the Guardian.

Mexico now has the highest child and adult obesity rates in the world and 14% of adults are diabetic.

It also has the highest per capita soda consumption rate in the world. Each year, Mexico’s 119 million people drink on average 163 litres of sugary fizzy drinks each, or nearly half a litre every day. Coca-Cola controls almost three quarters of the market.

A ground-breaking sugar tax on sugary drinks was introduced in January 2014 amid growing concerns about the obesity and diabetes epidemics. The 10% tax – which was implemented after a battle with the drinks industry – cut sales by 6% in the first year.

But the rules governing advertising and labelling in Mexico are relatively weak and the complaints procedure can be long and cumbersome. Even when companies are sanctioned, the fines are so small they do not serve as a deterrent, according to Alejandro Cavillo, director of Consumer Power.

Coca-Cola’s claim against the consumer rights law was thrown out in July, but the company promptly lodged an appeal.

The appeal court – which will assess the soundness of the July decision dismissing the unconstitutionality claim – usually takes five or six months to issue a ruling.

However, in October the case was sent for completion to an equivalent court in the state of Zacatecas. This means the final ruling – which could set a precedent - is unlikely until to come until mid-2016, until which Profeco’s hands are tied.

Activists claim Coca-Cola’s delay tactic is harming consumers who are increasingly bombarded with misleadingly information amid a global strategy by soft drinks companies try to portray certain products as healthier choices.

Meanwhile the Sidral “with apple juice” campaign ended at the beginning of August. The new campaign promotes it as a traditional, domestically-produced soda and does not make the same claims.

A Coca-Cola spokesman said: “To reinforce our commitment of encouraging informed purchase decisions, there was a modification of the logo and labelling. The percentage of juice contained in the product will be visible in the front part of the product, information that has always been present in the label.

“In this case we executed our right of defense as provided by law … it was not a delaying tactic.”

This is not the only Coke advert to draw complaint in Mexico. Earlier this month, the company issued an apology over a Christmas advert deemed offensive to the country’s indigenous population. The advert was withdrawn.