His domestic reputation has survived a brutal drug war that took thousands of lives, an attack on God as “stupid”, jokes about rape and a barrage of misogynistic comments.

But now the Philippine president, Rodrigo Duterte, faces the first serious dip in his popularity ratings amid soaring inflation, which has caused the price of some everyday items such as rice, bread and fuel to double.

Duterte’s attacks on his most vocal critics also received their first pushback from the courts this week, after a judge rejected the petition for the arrest of Senator Antonio Trillanes IV, one of the president’s fiercest opponents. The move was described as a “huge political slap” to the president.

Inflation in the Philippines, which was one of the fastest-growing economies in south-east Asia, stands at almost 7%, a nine-year record for the country and the highest in the region.

“Duterte has had dents in his popularity in the past, but in the past few months this has been the most sustained decline in his popularity,” said Maria Ela L Atienza, the editor of the Philippine Political Science Journal.

“The price of groceries is increasing, transportation is getting more expensive and in disarray, and the price of even basic foods like bread is increasing. A lot of people are angry and they are complaining because they are really feeling the effect of the rising cost of living.”

Facebook Twitter Pinterest Antonio Trillanes IV has been one of Duterte’s strongest critics. Photograph: Bullit Marquez/AP

Since he was elected in 2016, Duterte’s popularity rating had remained at about 80% due to his appeal to the biggest sections of voters – poor people in urban areas and the middle classes – many of whom praised his brash, often offensive style, which was seen as an antidote to “corrupt, imperial Manila”.

But his popularity has nosedived and is, by some estimates, at 50-60%, mainly because of a controversial tax policy. The Duterte administration introduced a levy that aimed to reduce national poverty to 14% but in fact increased the price of everyday goods with a value-added tax. It meant the cost of food rose by 10% in September, with fish up by 12% and vegetables by 20%. Some disgruntled shoppers reported loaves of bread being smaller.

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In the southern region of Zamboanga, a state of calamity was declared after a rice shortage caused prices to soar by a reported 75%. The situation became so severe nationwide that the government lifted restrictions on rice imports to try to relieve demand and bring prices down, but many say those policies have come too late and fail to address the long-term problem.

The rising price of fuel has also dealt a blow to poor people in urban areas; the situation is expected worsen when fares on public transport go up by a planned two pesos (3p) in November.

Duterte has largely refused to acknowledge his administration’s role in the crisis, instead blaming “corrupt” rice hoarders, the US-China trade war and rising global oil prices for the higher cost of living. Certainly Typhoon Mangkhut, which struck one of the most agricultural areas of the Philippines and destroyed more than 250,000 tonnes of rice, did not help matters, but critics have accused the government of not stockpiling adequately.

However, Atienza said the decline in Duterte’s popularity was also linked to the fact that though he had been in power for more than two years, significant pledges had not yet been fulfilled. “Duterte made the promise he would eliminate drugs in six months or one year but still no major drug dealers have been caught and a lot of people, including children, have died,” she said.

“Most of the promised infrastructure projects programme have not been fulfilled. A lot of people in the metro Manila area have a lot of problems with the mass transport system, and the conditions of the trains are very bad – and he has not eliminated the security problems with Islamic and communist insurgents in the south.”