The judiciary needs to be more diverse so that the public feel those on the bench are genuinely “our judges” rather than “beings from another planet”, the president of the supreme court has said.

In an interview to mark the centenary of the 1919 act that dismantled barriers preventing women from entering the professions, Lady Hale called for a more balanced gender representation on the UK’s highest court as well as swifter progress promoting those from minority ethnic backgrounds and with “less privileged lives”.

Women working in law and other professions are increasingly aware and resentful of earning less than men, said Hale, who is the court’s first female president since its creation 10 years ago. She also described the compulsory retirement age of 70 for judges as a “waste of talent”.

This year, 2019, marks the 10th anniversary of the creation of the supreme court. Hale said she believed in its first decade the court had improved the accessibility and transparency of the legal system while establishing its independence more “visibly”.

Based in a neo-gothic building opposite parliament, the supreme court has pioneered live-streaming its proceedings, welcomes visitors, holds public exhibitions and prints comprehensible summaries of its complex judgments.

Hale has supported the pursuit of gender equality as consistently as she can within the constitutional restraints of her position. There are currently three female justices on the UK’s 12-seat supreme court – a rapid advancement on the position up until mid-2017 when she was the only woman. But how many women should there be?

“Ruth Bader Ginsburg [the long-serving US supreme court justice, when asked the same question] famously said: ‘When there are nine’. There are [only] nine justices on the US supreme court bench,” Hale explained. “My own view is up to a quarter [on the UK supreme court] is an important breakthrough but that there’s no right number of justices of either gender. An ideal balance would be at least 60/40 either way. And so we still have a little way to go towards that.”

There are several reasons for desiring a more diverse judiciary in terms of gender balance, ethnicity and social background, Hale said. The most important of these is so the public can “look at the judges and say ‘They are our judges’,” rather than seeing them as “beings from another planet”.

In the high court, court of appeal and supreme court, a quarter of judges are women. Among district judges, around a third are female. Diversity, Hale said, also helps by bringing “different perspectives to the discussion”, particularly on a “collegiate” court. “We are all products of our background and our experiences, so the greater the diversity, the better.”

Having more than one woman on the supreme court had demonstrated that “women are as different to one another as men are” she said, acknowledging that it had been “refreshing” to sit with other women.

While overt discrimination is illegal, there remain hurdles to overcome. “We do have in this country a gender pay gap to worry about,” she said. “The more pay is [delivered] through individual negotiation rather than collective agreement, the greater the risk of imbalance.

“[Women] are just waking up to the fact that they are not being paid as much. I have heard terrible stories about even successful women barristers being offered out by their [chamber] clerks at less than their male equivalents. That’s an area where there’s still work to do.”

Sexual harassment has also caused problems for women at the bar, Hale said. She had not personally experienced problems during her career, she said, but was aware of its sexist culture – at least in the past.

“I do recall that when I was being elected to the northern circuit they required young women being elected to get on the table [as an initiation rite],” she said. “They didn’t require me to get on the table. [I don’t know] whether they thought I could not get up or whether [it was because] I was already married to a member of the circuit.”

More progress was needed in advancing people from ethnic minority backgrounds into the higher judiciary, Hale said. “It’s not surprising that [the pace of promotion] is slower: it is [only] more recently that members of ethnic minorities have joined the legal profession in larger numbers. Although there’s definitely a way to go, [the discrepancy] may not be as bad as we thought.”

There is already a strong presence of ethnic minority judges in tribunals, county courts and among district judges, she said. “The way we can try and improve diversity in the higher echelons is being more open to transfers from other [courts]. And there have been appointments from the upper tier [tribunals] to the high court. So that is beginning to happen [though] it’s still quite slow.”

She hoped the judiciary would attract “more people who have had less privileged lives”. Hale added: “I have had a privileged life [but] I don’t come from a privileged background and that is helpful. I have experienced various disappointments and setbacks in my life. I think all of this is quite helpful.”

Lady Hale does not approve of positive discrimination, chiefly because “no one wants to feel they have got the job in any way other than on their own merits”. Better outreach efforts to encourage candidates are more productive, she said.

Now 73, she is one of a small number of judges appointed before 1995 who are permitted to stay on the bench until they reach the age of 75. All those appointed since then have to retire at 70. Hale follows her predecessor, Lord Neuberger, in questioning that rule given the current shortage of high court judges.

“[He] called for the retirement age to go back to 75 and there’s obviously a case for that,” she said. “There’s a waste of talent.” It would help solve the “difficulty of recruiting to the high court bench so that people could be attracted after the most expensive years of life”, she said. “My husband sat until he was 75 in a … property tribunal and no one could possibly doubt he still had a huge amount to offer.”

The argument against extending the compulsory retirement age has been that it creates “bed blocking”, slowing the progress of younger judges up the career ladder.

“The longer the old, white men [stay on] … the fewer posts there are for the younger more diverse judges,” she said. “But given the recruitment problems, I’m not sure that holds good. It does seem rather sad in these days to have a [retirement] age of 70.”

This year the supreme court, having visited Edinburgh and Belfast, is due to sit in Wales. Hale, who was born in Yorkshire, would like to hear cases outside London in the north of England and the West Country.

One of her proudest moments, Hale said, was the article 50 case in 2016 that decided the course of Brexit amid a political and media furore. Following the high court decision, the judges were condemned as “enemies of the people” for ruling against the government.

“I’m proud of the [article 50, Gina] Miller case because it was a classic constitutional issue about what the government could do and what parliament could do,” Hale explained. “It was reminiscent of the 17th-century battle between parliament and the king. We were reinforcing principles that had been established then.”

Moving the law lords out of parliament and into a separate supreme court had made “judicial independence more visible”, she said. The way the media treated the article 50 case at the supreme court was very different to coverage of what happened in the high court, Hale said.

This month the supreme court will host a display celebrating the centenary of the Sex Disqualification (Removal) Act, which enabled women to join the legal profession and others.

After Brexit the supreme court is unlikely to continue referring questions about EU law to the European court of justice in Luxembourg. “We shall have to work it out for ourselves,” she said. “Whether it will be for the better or worse, we don’t know.”

• This article was amended on 2 January 2019 to note that 2019 marks the 10th anniversary of the supreme court and to add in more details from Hale’s interview reflecting on its achievements.