The EU has piled further pressure on Pakistan’s likely next prime minister, Imran Khan, after his country’s disputed general election, noting a “lack of equality of opportunity” and “systematic attempts to undermine the ruling party” ahead of the vote.

Michael Gahler, chief of the European Union election observer mission, told a press conference in Islamabad that his 120-strong team observed no rigging on election day – but in serious criticisms that will cast a shadow over the formation of the new Tehreek-e-Insaf (PTI) government led by the former international cricketer, Gahler said that pressure on the media, “far stronger” efforts than usual to encourage switching parties and “judicial conduct” had all negatively influenced the vote.

“We have concluded there was a lack of equality of opportunity,” he said, adding that the overall process was “not as good” as in 2013.

The Pakistan Muslim League-Nawaz (PML-N) party had complained that its election chances were badly hurt long before polling got under way. More than 30 of its candidates left the party during the campaign and many alleged privately that they had been pressured by Pakistan’s ISI spy agency.

After a meeting of six opposition parties on Friday Hamza Shahbaz Sharif, leader of the PML-N, said he would decide on Sunday whether or not to boycott parliament, stopping short of endorsing a demand for a re-election raised by five other smaller parties.



The meeting was called to discuss opposition party leaders’ response after all claimed the vote had been rigged and that their polling agents – workers who keep an eye on the count – had been evicted from ballot booths by security officials.



Sharif said he would discuss the call to reject the result with party leadership.



In his speech, Gahler advised all parties to pursue rigging allegations through legal channels, saying that his team, which visited 582 of 85,000 polling stations, had seen no evidence of military interference.



Play Video 0:43 Imran Khan addresses vote rigging allegations in Pakistan election victory – video

The PTI enjoyed success across the country, official results showed on Friday. With two seats left to count, more than a day after the result was due, the PTI had won 117 seats in the national assembly, the PML-N had taken 64 and the Pakistan People’s party 43.

Khan will still need to form a coalition to become prime minister, which requires at least 137 seats, but a single party winning contests across the country – in the north, south and in Punjab – is rare in Pakistani politics.



The ease with which the PTI can implement its policy agenda also received a significant boost from its strong performance in state-level elections.



As well as forming the federal government, the PTI’s capture of 118 seats in the provincial assembly of Punjab, the largest and wealthiest province, means it has a good chance of evicting the PML-N from the state government there, a stronghold that its leadership had been desperate to protect.

The Election Commission of Pakistan said turnout had dropped to 52%, a fall of two points on 2013. This had been expected following a low-energy campaign beset by allegations that the military was seeking to hobble the PML-N.

In a televised victory speech on Thursday, Khan struck a unifiying tone, pledging to lift up the poor and allow rigging claims to be investigated.

Sharif, who founded the PML-N, told his family from the prison cell where he is serving a 10-year sentence for corruption that he considered the result “stolen”.



Gen Asif Ghafoor, the army’s spokesperson, was criticised after tweeting: “You honour who You will and You humble who You will”, a verse from the Qur’an that was taken in some quarters as confirmation of the military’s support for Khan.

Facebook Twitter Pinterest Supporters of Imran Khan celebrate in Karachi. Photograph: Shahzaib Akber/EPA

The trickle of official results threw up surprises. Senior PML-N leaders performed worse than expected. The former prime minister Shahid Khaqan Abbasi, who took up the role after the ousting of Sharif, lost the two constituencies he was contesting.

The former finance minister Miftah Ismail posted on Twitter that he was “looking for work” after his defeat. Shahbaz Sharif, Nawaz’s brother and the new leader of the party, scraped into parliament after losing three of the four seats he contested.

Quick guide Pakistan elections: who are three main parties? Show Hide Pakistan Tehreek-e-Insaf (PTI) Also known as the Justice party, it is led by the former cricketer Imran Khan, and has had some success at provincial level but has never been able to convert it into national power. Khan has been accused both of lacking a coherent political philosophy and of sympathising with extremists. He has described the Taliban’s fight in Afghanistan as a holy war, and accused “liberals” who support Nato’s war on the group of being “thirsty for blood”.

Pakistan Muslim League-Nawaz Hopes to win control of parliament again, even though its leader, Nawaz Sharif, is in prison for corruption. Tried and sentenced in absentia, he returned to the country this month to serve his sentence, hoping to revitalise the campaign before the election. Now led by Sharif’s brother Shahbaz, the party is focusing on its economic success and promises of energy and infrastructure investment from China. However, efforts to increase tax revenues have faltered. Pakistan People’s party (PPP) Led by Bilawal Bhutto Zardari, son of the assassinated former prime minister Benazir Bhutto. The party lost ground after Benazir was killed in 2007 but the family name still carries considerable weight. The third-generation leader appears to be playing a long game, rebuilding support in its heartland with an eye on future elections. If it does well in this vote, the PPP could potentially serve as a junior partner in a coalition. Photograph: Aamir Qureshi/AFP

Although Tehreek-e-Labbaik, a new far-right Islamist party dedicated to killing blasphemers, failed to win any national seats, its strong second place in many contests raised fears that it will influence the future of Pakistani politics.

The party claimed a startling 10% of the vote in the 110-million strong province of Punjab, cutting into PML-N support, and won two seats in the Sindh provincial government.

Imran Khan has won over Pakistan. But real power still lies with the army | Samira Shackle Read more

The political analyst Umair Javed told the Guardian that the scale of Khan’s win across the country made the PTI a rare, “truly national party”. It won a two-thirds majority in the northern province of Khyber Pakhtunkhwa, the first since 1951, while at the other end of Pakistan, in the southern business capital of Karachi, the party vastly outperformed expectations to claim half the seats.



That might reflect a shift away from ethnicity-based politics in both regions, said Javed.

The former PML-N cabinet minister Khawaja Saad Rafique petitioned for a recount after his defeat to Khan in the Punjab capital of Lahore. He said the presiding officer at the polling station “rejected” many votes. At a party meeting on Thursday, the PML-N decided against boycotting parliament.